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+@Ci{$Id: manual.of,v 1.175 2018/06/18 19:17:35 roberto Exp $}
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+@C{[(-------------------------------------------------------------------------}
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+@manual{
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+
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+@sect1{@title{Introduction}
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+
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+Lua is a powerful, efficient, lightweight, embeddable scripting language.
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+It supports procedural programming,
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+object-oriented programming, functional programming,
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+data-driven programming, and data description.
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+
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+Lua combines simple procedural syntax with powerful data description
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+constructs based on associative arrays and extensible semantics.
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+Lua is dynamically typed,
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+runs by interpreting bytecode with a register-based
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+virtual machine,
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+and has automatic memory management with
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+incremental garbage collection,
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+making it ideal for configuration, scripting,
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+and rapid prototyping.
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+
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+Lua is implemented as a library, written in @emphx{clean C},
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+the common subset of @N{Standard C} and C++.
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+The Lua distribution includes a host program called @id{lua},
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+which uses the Lua library to offer a complete,
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+standalone Lua interpreter,
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+for interactive or batch use.
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+Lua is intended to be used both as a powerful, lightweight,
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+embeddable scripting language for any program that needs one,
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+and as a powerful but lightweight and efficient stand-alone language.
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+
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+As an extension language, Lua has no notion of a @Q{main} program:
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+it works @emph{embedded} in a host client,
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+called the @emph{embedding program} or simply the @emphx{host}.
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+(Frequently, this host is the stand-alone @id{lua} program.)
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+The host program can invoke functions to execute a piece of Lua code,
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+can write and read Lua variables,
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+and can register @N{C functions} to be called by Lua code.
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+Through the use of @N{C functions}, Lua can be augmented to cope with
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+a wide range of different domains,
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+thus creating customized programming languages sharing a syntactical framework.
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+
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+Lua is free software,
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+and is provided as usual with no guarantees,
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+as stated in its license.
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+The implementation described in this manual is available
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+at Lua's official web site, @id{www.lua.org}.
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+
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+Like any other reference manual,
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+this document is dry in places.
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+For a discussion of the decisions behind the design of Lua,
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+see the technical papers available at Lua's web site.
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+For a detailed introduction to programming in Lua,
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+see Roberto's book, @emphx{Programming in Lua}.
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+
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+}
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+
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+
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+@C{-------------------------------------------------------------------------}
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+@sect1{basic| @title{Basic Concepts}
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+
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+This section describes the basic concepts of the language.
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+
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+@sect2{TypesSec| @title{Values and Types}
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+
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+Lua is a dynamically typed language.
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+This means that
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+variables do not have types; only values do.
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+There are no type definitions in the language.
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+All values carry their own type.
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+
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+All values in Lua are first-class values.
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+This means that all values can be stored in variables,
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+passed as arguments to other functions, and returned as results.
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+
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+There are eight @x{basic types} in Lua:
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+@def{nil}, @def{boolean}, @def{number},
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+@def{string}, @def{function}, @def{userdata},
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+@def{thread}, and @def{table}.
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+The type @emph{nil} has one single value, @nil,
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+whose main property is to be different from any other value;
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+it usually represents the absence of a useful value.
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+The type @emph{boolean} has two values, @false and @true.
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+Both @nil and @false make a condition false;
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+any other value makes it true.
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+The type @emph{number} represents both
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+integer numbers and real (floating-point) numbers.
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+The type @emph{string} represents immutable sequences of bytes.
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+@index{eight-bit clean}
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+Lua is 8-bit clean:
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+strings can contain any 8-bit value,
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+including @x{embedded zeros} (@Char{\0}).
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+Lua is also encoding-agnostic;
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+it makes no assumptions about the contents of a string.
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+
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+The type @emph{number} uses two internal representations,
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+or two @x{subtypes},
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+one called @def{integer} and the other called @def{float}.
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+Lua has explicit rules about when each representation is used,
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+but it also converts between them automatically as needed @see{coercion}.
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+Therefore,
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+the programmer may choose to mostly ignore the difference
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+between integers and floats
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+or to assume complete control over the representation of each number.
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+Standard Lua uses 64-bit integers and double-precision (64-bit) floats,
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+but you can also compile Lua so that it
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+uses 32-bit integers and/or single-precision (32-bit) floats.
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+The option with 32 bits for both integers and floats
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+is particularly attractive
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+for small machines and embedded systems.
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+(See macro @id{LUA_32BITS} in file @id{luaconf.h}.)
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+
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+Lua can call (and manipulate) functions written in Lua and
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+functions written in C @see{functioncall}.
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+Both are represented by the type @emph{function}.
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+
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+The type @emph{userdata} is provided to allow arbitrary @N{C data} to
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+be stored in Lua variables.
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+A userdata value represents a block of raw memory.
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+There are two kinds of userdata:
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+@emphx{full userdata},
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+which is an object with a block of memory managed by Lua,
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+and @emphx{light userdata},
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+which is simply a @N{C pointer} value.
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+Userdata has no predefined operations in Lua,
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+except assignment and identity test.
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+By using @emph{metatables},
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+the programmer can define operations for full userdata values
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+@see{metatable}.
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+Userdata values cannot be created or modified in Lua,
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+only through the @N{C API}.
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+This guarantees the integrity of data owned by the host program.
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+
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+The type @def{thread} represents independent threads of execution
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+and it is used to implement coroutines @see{coroutine}.
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+Lua threads are not related to operating-system threads.
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+Lua supports coroutines on all systems,
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+even those that do not support threads natively.
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+
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+The type @emph{table} implements @x{associative arrays},
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+that is, @x{arrays} that can have as indices not only numbers,
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+but any Lua value except @nil and @x{NaN}.
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+(@emphx{Not a Number} is a special floating-point value
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+used by the @x{IEEE 754} standard to represent
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+undefined or unrepresentable numerical results, such as @T{0/0}.)
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+Tables can be @emph{heterogeneous};
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+that is, they can contain values of all types (except @nil).
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+Any key with value @nil is not considered part of the table.
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+Conversely, any key that is not part of a table has
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+an associated value @nil.
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+
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+Tables are the sole data-structuring mechanism in Lua;
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+they can be used to represent ordinary arrays, lists,
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+symbol tables, sets, records, graphs, trees, etc.
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+To represent @x{records}, Lua uses the field name as an index.
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+The language supports this representation by
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+providing @id{a.name} as syntactic sugar for @T{a["name"]}.
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+There are several convenient ways to create tables in Lua
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+@see{tableconstructor}.
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+
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+Like indices,
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+the values of table fields can be of any type.
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+In particular,
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+because functions are first-class values,
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+table fields can contain functions.
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+Thus tables can also carry @emph{methods} @see{func-def}.
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+
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+The indexing of tables follows
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+the definition of raw equality in the language.
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+The expressions @T{a[i]} and @T{a[j]}
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+denote the same table element
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+if and only if @id{i} and @id{j} are raw equal
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+(that is, equal without metamethods).
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+In particular, floats with integral values
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+are equal to their respective integers
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+(e.g., @T{1.0 == 1}).
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+To avoid ambiguities,
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+any float with integral value used as a key
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+is converted to its respective integer.
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+For instance, if you write @T{a[2.0] = true},
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+the actual key inserted into the table will be the
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+integer @T{2}.
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+(On the other hand,
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+2 and @St{2} are different Lua values and therefore
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+denote different table entries.)
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+
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+
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+Tables, functions, threads, and (full) userdata values are @emph{objects}:
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+variables do not actually @emph{contain} these values,
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+only @emph{references} to them.
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+Assignment, parameter passing, and function returns
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+always manipulate references to such values;
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+these operations do not imply any kind of copy.
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+
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+The library function @Lid{type} returns a string describing the type
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+of a given value @see{predefined}.
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+
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+}
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+
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+@sect2{globalenv| @title{Environments and the Global Environment}
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+
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+As will be discussed in @refsec{variables} and @refsec{assignment},
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+any reference to a free name
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+(that is, a name not bound to any declaration) @id{var}
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+is syntactically translated to @T{_ENV.var}.
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+Moreover, every chunk is compiled in the scope of
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+an external local variable named @id{_ENV} @see{chunks},
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+so @id{_ENV} itself is never a free name in a chunk.
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+
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+Despite the existence of this external @id{_ENV} variable and
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+the translation of free names,
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+@id{_ENV} is a completely regular name.
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+In particular,
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+you can define new variables and parameters with that name.
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+Each reference to a free name uses the @id{_ENV} that is
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+visible at that point in the program,
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+following the usual visibility rules of Lua @see{visibility}.
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+
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+Any table used as the value of @id{_ENV} is called an @def{environment}.
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+
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+Lua keeps a distinguished environment called the @def{global environment}.
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+This value is kept at a special index in the C registry @see{registry}.
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+In Lua, the global variable @Lid{_G} is initialized with this same value.
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+(@Lid{_G} is never used internally.)
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+
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+When Lua loads a chunk,
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+the default value for its @id{_ENV} upvalue
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+is the global environment @seeF{load}.
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+Therefore, by default,
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+free names in Lua code refer to entries in the global environment
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+(and, therefore, they are also called @def{global variables}).
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+Moreover, all standard libraries are loaded in the global environment
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+and some functions there operate on that environment.
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+You can use @Lid{load} (or @Lid{loadfile})
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+to load a chunk with a different environment.
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+(In C, you have to load the chunk and then change the value
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+of its first upvalue.)
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+
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+}
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+
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+@sect2{error| @title{Error Handling}
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+
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+Because Lua is an embedded extension language,
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+all Lua actions start from @N{C code} in the host program
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+calling a function from the Lua library.
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+(When you use Lua standalone,
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+the @id{lua} application is the host program.)
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+Whenever an error occurs during
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+the compilation or execution of a Lua chunk,
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+control returns to the host,
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+which can take appropriate measures
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+(such as printing an error message).
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+
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+Lua code can explicitly generate an error by calling the
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+@Lid{error} function.
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+If you need to catch errors in Lua,
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+you can use @Lid{pcall} or @Lid{xpcall}
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+to call a given function in @emphx{protected mode}.
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+
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+Whenever there is an error,
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+an @def{error object} (also called an @def{error message})
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+is propagated with information about the error.
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+Lua itself only generates errors whose error object is a string,
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+but programs may generate errors with
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+any value as the error object.
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+It is up to the Lua program or its host to handle such error objects.
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+
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+
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+When you use @Lid{xpcall} or @Lid{lua_pcall},
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+you may give a @def{message handler}
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+to be called in case of errors.
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+This function is called with the original error object
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+and returns a new error object.
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+It is called before the error unwinds the stack,
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+so that it can gather more information about the error,
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+for instance by inspecting the stack and creating a stack traceback.
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+This message handler is still protected by the protected call;
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+so, an error inside the message handler
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+will call the message handler again.
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+If this loop goes on for too long,
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+Lua breaks it and returns an appropriate message.
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+(The message handler is called only for regular runtime errors.
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+It is not called for memory-allocation errors
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+nor for errors while running finalizers.)
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+
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+}
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+
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+@sect2{metatable| @title{Metatables and Metamethods}
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+
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+Every value in Lua can have a @emph{metatable}.
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+This @def{metatable} is an ordinary Lua table
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+that defines the behavior of the original value
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+under certain special operations.
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+You can change several aspects of the behavior
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+of operations over a value by setting specific fields in its metatable.
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+For instance, when a non-numeric value is the operand of an addition,
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+Lua checks for a function in the field @St{__add} of the value's metatable.
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+If it finds one,
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+Lua calls this function to perform the addition.
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+
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+The key for each event in a metatable is a string
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+with the event name prefixed by two underscores;
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+the corresponding values are called @def{metamethods}.
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+In the previous example, the key is @St{__add}
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+and the metamethod is the function that performs the addition.
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+Unless stated otherwise,
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+metamethods should be function values.
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+
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+You can query the metatable of any value
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+using the @Lid{getmetatable} function.
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+Lua queries metamethods in metatables using a raw access @seeF{rawget}.
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+So, to retrieve the metamethod for event @id{ev} in object @id{o},
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+Lua does the equivalent to the following code:
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+@verbatim{
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+rawget(getmetatable(@rep{o}) or {}, "__@rep{ev}")
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+}
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+
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+You can replace the metatable of tables
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+using the @Lid{setmetatable} function.
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+You cannot change the metatable of other types from Lua code
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+(except by using the @link{debuglib|debug library});
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+you should use the @N{C API} for that.
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+
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+Tables and full userdata have individual metatables
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+(although multiple tables and userdata can share their metatables).
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+Values of all other types share one single metatable per type;
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+that is, there is one single metatable for all numbers,
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+one for all strings, etc.
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+By default, a value has no metatable,
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+but the string library sets a metatable for the string type @see{strlib}.
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+
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+A metatable controls how an object behaves in
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+arithmetic operations, bitwise operations,
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+order comparisons, concatenation, length operation, calls, and indexing.
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+A metatable also can define a function to be called
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+when a userdata or a table is @link{GC|garbage collected}.
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+
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+For the unary operators (negation, length, and bitwise NOT),
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+the metamethod is computed and called with a dummy second operand,
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+equal to the first one.
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+This extra operand is only to simplify Lua's internals
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+(by making these operators behave like a binary operation)
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+and may be removed in future versions.
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+(For most uses this extra operand is irrelevant.)
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+
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+A detailed list of events controlled by metatables is given next.
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+Each operation is identified by its corresponding key.
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+
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+@description{
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+
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+@item{@idx{__add}|
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+the addition (@T{+}) operation.
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+If any operand for an addition is not a number
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+(nor a string coercible to a number),
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+Lua will try to call a metamethod.
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+First, Lua will check the first operand (even if it is valid).
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+If that operand does not define a metamethod for @idx{__add},
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+then Lua will check the second operand.
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+If Lua can find a metamethod,
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+it calls the metamethod with the two operands as arguments,
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+and the result of the call
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+(adjusted to one value)
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+is the result of the operation.
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+Otherwise,
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+it raises an error.
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+}
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+
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+@item{@idx{__sub}|
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+the subtraction (@T{-}) operation.
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+Behavior similar to the addition operation.
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+}
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+
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+@item{@idx{__mul}|
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+the multiplication (@T{*}) operation.
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+Behavior similar to the addition operation.
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+}
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+
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+@item{@idx{__div}|
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+the division (@T{/}) operation.
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+Behavior similar to the addition operation.
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+}
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+
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+@item{@idx{__mod}|
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+the modulo (@T{%}) operation.
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+Behavior similar to the addition operation.
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+}
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+
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|
+@item{@idx{__pow}|
|
|
|
+the exponentiation (@T{^}) operation.
|
|
|
+Behavior similar to the addition operation.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__unm}|
|
|
|
+the negation (unary @T{-}) operation.
|
|
|
+Behavior similar to the addition operation.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__idiv}|
|
|
|
+the floor division (@T{//}) operation.
|
|
|
+Behavior similar to the addition operation.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__band}|
|
|
|
+the bitwise AND (@T{&}) operation.
|
|
|
+Behavior similar to the addition operation,
|
|
|
+except that Lua will try a metamethod
|
|
|
+if any operand is neither an integer
|
|
|
+nor a value coercible to an integer @see{coercion}.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__bor}|
|
|
|
+the bitwise OR (@T{|}) operation.
|
|
|
+Behavior similar to the bitwise AND operation.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__bxor}|
|
|
|
+the bitwise exclusive OR (binary @T{~}) operation.
|
|
|
+Behavior similar to the bitwise AND operation.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__bnot}|
|
|
|
+the bitwise NOT (unary @T{~}) operation.
|
|
|
+Behavior similar to the bitwise AND operation.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__shl}|
|
|
|
+the bitwise left shift (@T{<<}) operation.
|
|
|
+Behavior similar to the bitwise AND operation.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__shr}|
|
|
|
+the bitwise right shift (@T{>>}) operation.
|
|
|
+Behavior similar to the bitwise AND operation.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__concat}|
|
|
|
+the concatenation (@T{..}) operation.
|
|
|
+Behavior similar to the addition operation,
|
|
|
+except that Lua will try a metamethod
|
|
|
+if any operand is neither a string nor a number
|
|
|
+(which is always coercible to a string).
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__len}|
|
|
|
+the length (@T{#}) operation.
|
|
|
+If the object is not a string,
|
|
|
+Lua will try its metamethod.
|
|
|
+If there is a metamethod,
|
|
|
+Lua calls it with the object as argument,
|
|
|
+and the result of the call
|
|
|
+(always adjusted to one value)
|
|
|
+is the result of the operation.
|
|
|
+If there is no metamethod but the object is a table,
|
|
|
+then Lua uses the table length operation @see{len-op}.
|
|
|
+Otherwise, Lua raises an error.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__eq}|
|
|
|
+the equal (@T{==}) operation.
|
|
|
+Behavior similar to the addition operation,
|
|
|
+except that Lua will try a metamethod only when the values
|
|
|
+being compared are either both tables or both full userdata
|
|
|
+and they are not primitively equal.
|
|
|
+The result of the call is always converted to a boolean.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__lt}|
|
|
|
+the less than (@T{<}) operation.
|
|
|
+Behavior similar to the addition operation,
|
|
|
+except that Lua will try a metamethod only when the values
|
|
|
+being compared are neither both numbers nor both strings.
|
|
|
+The result of the call is always converted to a boolean.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__le}|
|
|
|
+the less equal (@T{<=}) operation.
|
|
|
+Unlike other operations,
|
|
|
+the less-equal operation can use two different events.
|
|
|
+First, Lua looks for the @idx{__le} metamethod in both operands,
|
|
|
+like in the less than operation.
|
|
|
+If it cannot find such a metamethod,
|
|
|
+then it will try the @idx{__lt} metamethod,
|
|
|
+assuming that @T{a <= b} is equivalent to @T{not (b < a)}.
|
|
|
+As with the other comparison operators,
|
|
|
+the result is always a boolean.
|
|
|
+(This use of the @idx{__lt} event can be removed in future versions;
|
|
|
+it is also slower than a real @idx{__le} metamethod.)
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__index}|
|
|
|
+The indexing access operation @T{table[key]}.
|
|
|
+This event happens when @id{table} is not a table or
|
|
|
+when @id{key} is not present in @id{table}.
|
|
|
+The metamethod is looked up in @id{table}.
|
|
|
+
|
|
|
+Despite the name,
|
|
|
+the metamethod for this event can be either a function or a table.
|
|
|
+If it is a function,
|
|
|
+it is called with @id{table} and @id{key} as arguments,
|
|
|
+and the result of the call
|
|
|
+(adjusted to one value)
|
|
|
+is the result of the operation.
|
|
|
+If it is a table,
|
|
|
+the final result is the result of indexing this table with @id{key}.
|
|
|
+(This indexing is regular, not raw,
|
|
|
+and therefore can trigger another metamethod.)
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__newindex}|
|
|
|
+The indexing assignment @T{table[key] = value}.
|
|
|
+Like the index event,
|
|
|
+this event happens when @id{table} is not a table or
|
|
|
+when @id{key} is not present in @id{table}.
|
|
|
+The metamethod is looked up in @id{table}.
|
|
|
+
|
|
|
+Like with indexing,
|
|
|
+the metamethod for this event can be either a function or a table.
|
|
|
+If it is a function,
|
|
|
+it is called with @id{table}, @id{key}, and @id{value} as arguments.
|
|
|
+If it is a table,
|
|
|
+Lua does an indexing assignment to this table with the same key and value.
|
|
|
+(This assignment is regular, not raw,
|
|
|
+and therefore can trigger another metamethod.)
|
|
|
+
|
|
|
+Whenever there is a @idx{__newindex} metamethod,
|
|
|
+Lua does not perform the primitive assignment.
|
|
|
+(If necessary,
|
|
|
+the metamethod itself can call @Lid{rawset}
|
|
|
+to do the assignment.)
|
|
|
+}
|
|
|
+
|
|
|
+@item{@idx{__call}|
|
|
|
+The call operation @T{func(args)}.
|
|
|
+This event happens when Lua tries to call a non-function value
|
|
|
+(that is, @id{func} is not a function).
|
|
|
+The metamethod is looked up in @id{func}.
|
|
|
+If present,
|
|
|
+the metamethod is called with @id{func} as its first argument,
|
|
|
+followed by the arguments of the original call (@id{args}).
|
|
|
+All results of the call
|
|
|
+are the result of the operation.
|
|
|
+(This is the only metamethod that allows multiple results.)
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+It is a good practice to add all needed metamethods to a table
|
|
|
+before setting it as a metatable of some object.
|
|
|
+In particular, the @idx{__gc} metamethod works only when this order
|
|
|
+is followed @see{finalizers}.
|
|
|
+
|
|
|
+Because metatables are regular tables,
|
|
|
+they can contain arbitrary fields,
|
|
|
+not only the event names defined above.
|
|
|
+Some functions in the standard library
|
|
|
+(e.g., @Lid{tostring})
|
|
|
+use other fields in metatables for their own purposes.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{GC| @title{Garbage Collection}
|
|
|
+
|
|
|
+Lua performs automatic memory management.
|
|
|
+This means that
|
|
|
+you do not have to worry about allocating memory for new objects
|
|
|
+or freeing it when the objects are no longer needed.
|
|
|
+Lua manages memory automatically by running
|
|
|
+a @def{garbage collector} to collect all @emph{dead objects}
|
|
|
+(that is, objects that are no longer accessible from Lua).
|
|
|
+All memory used by Lua is subject to automatic management:
|
|
|
+strings, tables, userdata, functions, threads, internal structures, etc.
|
|
|
+
|
|
|
+The garbage collector (GC) in Lua can work in two modes:
|
|
|
+incremental and generational.
|
|
|
+
|
|
|
+The default GC mode with the default parameters
|
|
|
+are adequate for most uses.
|
|
|
+Programs that waste a large proportion of its time
|
|
|
+allocating and freeing memory can benefit from other settings.
|
|
|
+Keep in mind that the GC behavior is non-portable
|
|
|
+both across platforms and across different Lua releases;
|
|
|
+therefore, optimal settings are also non-portable.
|
|
|
+
|
|
|
+You can change the GC mode and parameters by calling
|
|
|
+@Lid{lua_gc} in C
|
|
|
+or @Lid{collectgarbage} in Lua.
|
|
|
+You can also use these functions to control
|
|
|
+the collector directly (e.g., stop and restart it).
|
|
|
+
|
|
|
+@sect3{@title{Incremental Garbage Collection}
|
|
|
+
|
|
|
+In incremental mode,
|
|
|
+each GC cycle performs a mark-and-sweep collection in small steps
|
|
|
+interleaved with the program's execution.
|
|
|
+In this mode,
|
|
|
+the collector uses three numbers to control its garbage-collection cycles:
|
|
|
+the @def{garbage-collector pause},
|
|
|
+the @def{garbage-collector step multiplier},
|
|
|
+and the @def{garbage-collector step size}.
|
|
|
+
|
|
|
+The garbage-collector pause
|
|
|
+controls how long the collector waits before starting a new cycle.
|
|
|
+The collector starts a new cycle when the use of memory
|
|
|
+hits @M{n%} of the use after the previous collection.
|
|
|
+Larger values make the collector less aggressive.
|
|
|
+Values smaller than 100 mean the collector will not wait to
|
|
|
+start a new cycle.
|
|
|
+A value of 200 means that the collector waits for the total memory in use
|
|
|
+to double before starting a new cycle.
|
|
|
+The default value is 200; the maximum value is 1000.
|
|
|
+
|
|
|
+The garbage-collector step multiplier
|
|
|
+controls the relative speed of the collector relative to
|
|
|
+memory allocation,
|
|
|
+that is,
|
|
|
+how many elements it marks or sweeps for each
|
|
|
+kilobyte of memory allocated.
|
|
|
+Larger values make the collector more aggressive but also increase
|
|
|
+the size of each incremental step.
|
|
|
+You should not use values smaller than 100,
|
|
|
+because they make the collector too slow and
|
|
|
+can result in the collector never finishing a cycle.
|
|
|
+The default value is 100; the maximum value is 1000.
|
|
|
+
|
|
|
+The garbage-collector step size controls the
|
|
|
+size of each incremental step,
|
|
|
+specifically how many bytes the interpreter allocates
|
|
|
+before performing a step.
|
|
|
+This parameter is logarithmic:
|
|
|
+A value of @M{n} means the interpreter will allocate @M{2@sp{n}}
|
|
|
+bytes between steps and perform equivalent work during the step.
|
|
|
+A large value (e.g., 60) makes the collector a stop-the-world
|
|
|
+(non-incremental) collector.
|
|
|
+The default value is 13,
|
|
|
+which makes for steps of approximately @N{8 Kbytes}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{@title{Generational Garbage Collection}
|
|
|
+
|
|
|
+In generational mode,
|
|
|
+the collector does frequent @emph{minor} collections,
|
|
|
+which traverses only objects recently created.
|
|
|
+If after a minor collection the use of memory is still above a limit,
|
|
|
+the collector does a @emph{major} collection,
|
|
|
+which traverses all objects.
|
|
|
+The generational mode uses two parameters:
|
|
|
+the @def{major multiplier} and the @def{the minor multiplier}.
|
|
|
+
|
|
|
+The major multiplier controls the frequency of major collections.
|
|
|
+For a major multiplier @M{x},
|
|
|
+a new major collection will be done when memory
|
|
|
+grows @M{x%} larger than the memory in use after the previous major
|
|
|
+collection.
|
|
|
+For instance, for a multiplier of 100,
|
|
|
+the collector will do a major collection when the use of memory
|
|
|
+gets larger than twice the use after the previous collection.
|
|
|
+The default value is 100; the maximum value is 1000.
|
|
|
+
|
|
|
+The minor multiplier controls the frequency of minor collections.
|
|
|
+For a minor multiplier @M{x},
|
|
|
+a new minor collection will be done when memory
|
|
|
+grows @M{x%} larger than the memory in use after the previous major
|
|
|
+collection.
|
|
|
+For instance, for a multiplier of 20,
|
|
|
+the collector will do a minor collection when the use of memory
|
|
|
+gets 20% larger than the use after the previous major collection.
|
|
|
+The default value is 20; the maximum value is 200.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{finalizers| @title{Garbage-Collection Metamethods}
|
|
|
+
|
|
|
+You can set garbage-collector metamethods for tables
|
|
|
+and, using the @N{C API},
|
|
|
+for full userdata @see{metatable}.
|
|
|
+These metamethods are also called @def{finalizers}.
|
|
|
+Finalizers allow you to coordinate Lua's garbage collection
|
|
|
+with external resource management
|
|
|
+(such as closing files, network or database connections,
|
|
|
+or freeing your own memory).
|
|
|
+
|
|
|
+For an object (table or userdata) to be finalized when collected,
|
|
|
+you must @emph{mark} it for finalization.
|
|
|
+@index{mark (for finalization)}
|
|
|
+You mark an object for finalization when you set its metatable
|
|
|
+and the metatable has a field indexed by the string @St{__gc}.
|
|
|
+Note that if you set a metatable without a @idx{__gc} field
|
|
|
+and later create that field in the metatable,
|
|
|
+the object will not be marked for finalization.
|
|
|
+
|
|
|
+When a marked object becomes garbage,
|
|
|
+it is not collected immediately by the garbage collector.
|
|
|
+Instead, Lua puts it in a list.
|
|
|
+After the collection,
|
|
|
+Lua goes through that list.
|
|
|
+For each object in the list,
|
|
|
+it checks the object's @idx{__gc} metamethod:
|
|
|
+If it is a function,
|
|
|
+Lua calls it with the object as its single argument;
|
|
|
+if the metamethod is not a function,
|
|
|
+Lua simply ignores it.
|
|
|
+
|
|
|
+At the end of each garbage-collection cycle,
|
|
|
+the finalizers for objects are called in
|
|
|
+the reverse order that the objects were marked for finalization,
|
|
|
+among those collected in that cycle;
|
|
|
+that is, the first finalizer to be called is the one associated
|
|
|
+with the object marked last in the program.
|
|
|
+The execution of each finalizer may occur at any point during
|
|
|
+the execution of the regular code.
|
|
|
+
|
|
|
+Because the object being collected must still be used by the finalizer,
|
|
|
+that object (and other objects accessible only through it)
|
|
|
+must be @emph{resurrected} by Lua.@index{resurrection}
|
|
|
+Usually, this resurrection is transient,
|
|
|
+and the object memory is freed in the next garbage-collection cycle.
|
|
|
+However, if the finalizer stores the object in some global place
|
|
|
+(e.g., a global variable),
|
|
|
+then the resurrection is permanent.
|
|
|
+Moreover, if the finalizer marks a finalizing object for finalization again,
|
|
|
+its finalizer will be called again in the next cycle where the
|
|
|
+object is unreachable.
|
|
|
+In any case,
|
|
|
+the object memory is freed only in a GC cycle where
|
|
|
+the object is unreachable and not marked for finalization.
|
|
|
+
|
|
|
+When you close a state @seeF{lua_close},
|
|
|
+Lua calls the finalizers of all objects marked for finalization,
|
|
|
+following the reverse order that they were marked.
|
|
|
+If any finalizer marks objects for collection during that phase,
|
|
|
+these marks have no effect.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{weak-table| @title{Weak Tables}
|
|
|
+
|
|
|
+A @def{weak table} is a table whose elements are
|
|
|
+@def{weak references}.
|
|
|
+A weak reference is ignored by the garbage collector.
|
|
|
+In other words,
|
|
|
+if the only references to an object are weak references,
|
|
|
+then the garbage collector will collect that object.
|
|
|
+
|
|
|
+A weak table can have weak keys, weak values, or both.
|
|
|
+A table with weak values allows the collection of its values,
|
|
|
+but prevents the collection of its keys.
|
|
|
+A table with both weak keys and weak values allows the collection of
|
|
|
+both keys and values.
|
|
|
+In any case, if either the key or the value is collected,
|
|
|
+the whole pair is removed from the table.
|
|
|
+The weakness of a table is controlled by the
|
|
|
+@idx{__mode} field of its metatable.
|
|
|
+This field, if present, must be one of the following strings:
|
|
|
+@St{k}, for a table with weak keys;
|
|
|
+@St{v}, for a table with weak values;
|
|
|
+or @St{kv}, for a table with both weak keys and values.
|
|
|
+
|
|
|
+A table with weak keys and strong values
|
|
|
+is also called an @def{ephemeron table}.
|
|
|
+In an ephemeron table,
|
|
|
+a value is considered reachable only if its key is reachable.
|
|
|
+In particular,
|
|
|
+if the only reference to a key comes through its value,
|
|
|
+the pair is removed.
|
|
|
+
|
|
|
+Any change in the weakness of a table may take effect only
|
|
|
+at the next collect cycle.
|
|
|
+In particular, if you change the weakness to a stronger mode,
|
|
|
+Lua may still collect some items from that table
|
|
|
+before the change takes effect.
|
|
|
+
|
|
|
+Only objects that have an explicit construction
|
|
|
+are removed from weak tables.
|
|
|
+Values, such as numbers and @x{light @N{C functions}},
|
|
|
+are not subject to garbage collection,
|
|
|
+and therefore are not removed from weak tables
|
|
|
+(unless their associated values are collected).
|
|
|
+Although strings are subject to garbage collection,
|
|
|
+they do not have an explicit construction,
|
|
|
+and therefore are not removed from weak tables.
|
|
|
+
|
|
|
+Resurrected objects
|
|
|
+(that is, objects being finalized
|
|
|
+and objects accessible only through objects being finalized)
|
|
|
+have a special behavior in weak tables.
|
|
|
+They are removed from weak values before running their finalizers,
|
|
|
+but are removed from weak keys only in the next collection
|
|
|
+after running their finalizers, when such objects are actually freed.
|
|
|
+This behavior allows the finalizer to access properties
|
|
|
+associated with the object through weak tables.
|
|
|
+
|
|
|
+If a weak table is among the resurrected objects in a collection cycle,
|
|
|
+it may not be properly cleared until the next cycle.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{coroutine| @title{Coroutines}
|
|
|
+
|
|
|
+Lua supports coroutines,
|
|
|
+also called @emphx{collaborative multithreading}.
|
|
|
+A coroutine in Lua represents an independent thread of execution.
|
|
|
+Unlike threads in multithread systems, however,
|
|
|
+a coroutine only suspends its execution by explicitly calling
|
|
|
+a yield function.
|
|
|
+
|
|
|
+You create a coroutine by calling @Lid{coroutine.create}.
|
|
|
+Its sole argument is a function
|
|
|
+that is the main function of the coroutine.
|
|
|
+The @id{create} function only creates a new coroutine and
|
|
|
+returns a handle to it (an object of type @emph{thread});
|
|
|
+it does not start the coroutine.
|
|
|
+
|
|
|
+You execute a coroutine by calling @Lid{coroutine.resume}.
|
|
|
+When you first call @Lid{coroutine.resume},
|
|
|
+passing as its first argument
|
|
|
+a thread returned by @Lid{coroutine.create},
|
|
|
+the coroutine starts its execution by
|
|
|
+calling its main function.
|
|
|
+Extra arguments passed to @Lid{coroutine.resume} are passed
|
|
|
+as arguments to that function.
|
|
|
+After the coroutine starts running,
|
|
|
+it runs until it terminates or @emph{yields}.
|
|
|
+
|
|
|
+A coroutine can terminate its execution in two ways:
|
|
|
+normally, when its main function returns
|
|
|
+(explicitly or implicitly, after the last instruction);
|
|
|
+and abnormally, if there is an unprotected error.
|
|
|
+In case of normal termination,
|
|
|
+@Lid{coroutine.resume} returns @true,
|
|
|
+plus any values returned by the coroutine main function.
|
|
|
+In case of errors, @Lid{coroutine.resume} returns @false
|
|
|
+plus an error object.
|
|
|
+
|
|
|
+A coroutine yields by calling @Lid{coroutine.yield}.
|
|
|
+When a coroutine yields,
|
|
|
+the corresponding @Lid{coroutine.resume} returns immediately,
|
|
|
+even if the yield happens inside nested function calls
|
|
|
+(that is, not in the main function,
|
|
|
+but in a function directly or indirectly called by the main function).
|
|
|
+In the case of a yield, @Lid{coroutine.resume} also returns @true,
|
|
|
+plus any values passed to @Lid{coroutine.yield}.
|
|
|
+The next time you resume the same coroutine,
|
|
|
+it continues its execution from the point where it yielded,
|
|
|
+with the call to @Lid{coroutine.yield} returning any extra
|
|
|
+arguments passed to @Lid{coroutine.resume}.
|
|
|
+
|
|
|
+Like @Lid{coroutine.create},
|
|
|
+the @Lid{coroutine.wrap} function also creates a coroutine,
|
|
|
+but instead of returning the coroutine itself,
|
|
|
+it returns a function that, when called, resumes the coroutine.
|
|
|
+Any arguments passed to this function
|
|
|
+go as extra arguments to @Lid{coroutine.resume}.
|
|
|
+@Lid{coroutine.wrap} returns all the values returned by @Lid{coroutine.resume},
|
|
|
+except the first one (the boolean error code).
|
|
|
+Unlike @Lid{coroutine.resume},
|
|
|
+@Lid{coroutine.wrap} does not catch errors;
|
|
|
+any error is propagated to the caller.
|
|
|
+
|
|
|
+As an example of how coroutines work,
|
|
|
+consider the following code:
|
|
|
+@verbatim{
|
|
|
+function foo (a)
|
|
|
+ print("foo", a)
|
|
|
+ return coroutine.yield(2*a)
|
|
|
+end
|
|
|
+
|
|
|
+co = coroutine.create(function (a,b)
|
|
|
+ print("co-body", a, b)
|
|
|
+ local r = foo(a+1)
|
|
|
+ print("co-body", r)
|
|
|
+ local r, s = coroutine.yield(a+b, a-b)
|
|
|
+ print("co-body", r, s)
|
|
|
+ return b, "end"
|
|
|
+end)
|
|
|
+
|
|
|
+print("main", coroutine.resume(co, 1, 10))
|
|
|
+print("main", coroutine.resume(co, "r"))
|
|
|
+print("main", coroutine.resume(co, "x", "y"))
|
|
|
+print("main", coroutine.resume(co, "x", "y"))
|
|
|
+}
|
|
|
+When you run it, it produces the following output:
|
|
|
+@verbatim{
|
|
|
+co-body 1 10
|
|
|
+foo 2
|
|
|
+main true 4
|
|
|
+co-body r
|
|
|
+main true 11 -9
|
|
|
+co-body x y
|
|
|
+main true 10 end
|
|
|
+main false cannot resume dead coroutine
|
|
|
+}
|
|
|
+
|
|
|
+You can also create and manipulate coroutines through the C API:
|
|
|
+see functions @Lid{lua_newthread}, @Lid{lua_resume},
|
|
|
+and @Lid{lua_yield}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@C{-------------------------------------------------------------------------}
|
|
|
+@sect1{language| @title{The Language}
|
|
|
+
|
|
|
+This section describes the lexis, the syntax, and the semantics of Lua.
|
|
|
+In other words,
|
|
|
+this section describes
|
|
|
+which tokens are valid,
|
|
|
+how they can be combined,
|
|
|
+and what their combinations mean.
|
|
|
+
|
|
|
+Language constructs will be explained using the usual extended BNF notation,
|
|
|
+in which
|
|
|
+@N{@bnfrep{@rep{a}} means 0} or more @rep{a}'s, and
|
|
|
+@N{@bnfopt{@rep{a}} means} an optional @rep{a}.
|
|
|
+Non-terminals are shown like @bnfNter{non-terminal},
|
|
|
+keywords are shown like @rw{kword},
|
|
|
+and other terminal symbols are shown like @bnfter{=}.
|
|
|
+The complete syntax of Lua can be found in @refsec{BNF}
|
|
|
+at the end of this manual.
|
|
|
+
|
|
|
+@sect2{lexical| @title{Lexical Conventions}
|
|
|
+
|
|
|
+Lua is a @x{free-form} language.
|
|
|
+It ignores spaces (including new lines) and comments
|
|
|
+between lexical elements (@x{tokens}),
|
|
|
+except as delimiters between @x{names} and @x{keywords}.
|
|
|
+
|
|
|
+@def{Names}
|
|
|
+(also called @def{identifiers})
|
|
|
+in Lua can be any string of letters,
|
|
|
+digits, and underscores,
|
|
|
+not beginning with a digit and
|
|
|
+not being a reserved word.
|
|
|
+Identifiers are used to name variables, table fields, and labels.
|
|
|
+
|
|
|
+The following @def{keywords} are reserved
|
|
|
+and cannot be used as names:
|
|
|
+@index{reserved words}
|
|
|
+@verbatim{
|
|
|
+and break do else elseif end
|
|
|
+false for function goto if in
|
|
|
+local nil not or repeat return
|
|
|
+then true until while
|
|
|
+}
|
|
|
+
|
|
|
+Lua is a case-sensitive language:
|
|
|
+@id{and} is a reserved word, but @id{And} and @id{AND}
|
|
|
+are two different, valid names.
|
|
|
+As a convention,
|
|
|
+programs should avoid creating
|
|
|
+names that start with an underscore followed by
|
|
|
+one or more uppercase letters (such as @Lid{_VERSION}).
|
|
|
+
|
|
|
+The following strings denote other @x{tokens}:
|
|
|
+@verbatim{
|
|
|
++ - * / % ^ #
|
|
|
+& ~ | << >> //
|
|
|
+== ~= <= >= < > =
|
|
|
+( ) { } [ ] ::
|
|
|
+; : , . .. ...
|
|
|
+}
|
|
|
+
|
|
|
+A @def{short literal string}
|
|
|
+can be delimited by matching single or double quotes,
|
|
|
+and can contain the following C-like escape sequences:
|
|
|
+@Char{\a} (bell),
|
|
|
+@Char{\b} (backspace),
|
|
|
+@Char{\f} (form feed),
|
|
|
+@Char{\n} (newline),
|
|
|
+@Char{\r} (carriage return),
|
|
|
+@Char{\t} (horizontal tab),
|
|
|
+@Char{\v} (vertical tab),
|
|
|
+@Char{\\} (backslash),
|
|
|
+@Char{\"} (quotation mark [double quote]),
|
|
|
+and @Char{\'} (apostrophe [single quote]).
|
|
|
+A backslash followed by a line break
|
|
|
+results in a newline in the string.
|
|
|
+The escape sequence @Char{\z} skips the following span
|
|
|
+of white-space characters,
|
|
|
+including line breaks;
|
|
|
+it is particularly useful to break and indent a long literal string
|
|
|
+into multiple lines without adding the newlines and spaces
|
|
|
+into the string contents.
|
|
|
+A short literal string cannot contain unescaped line breaks
|
|
|
+nor escapes not forming a valid escape sequence.
|
|
|
+
|
|
|
+We can specify any byte in a short literal string,
|
|
|
+including @x{embedded zeros},
|
|
|
+by its numeric value.
|
|
|
+This can be done
|
|
|
+with the escape sequence @T{\x@rep{XX}},
|
|
|
+where @rep{XX} is a sequence of exactly two hexadecimal digits,
|
|
|
+or with the escape sequence @T{\@rep{ddd}},
|
|
|
+where @rep{ddd} is a sequence of up to three decimal digits.
|
|
|
+(Note that if a decimal escape sequence is to be followed by a digit,
|
|
|
+it must be expressed using exactly three digits.)
|
|
|
+
|
|
|
+The @x{UTF-8} encoding of a @x{Unicode} character
|
|
|
+can be inserted in a literal string with
|
|
|
+the escape sequence @T{\u{@rep{XXX}}}
|
|
|
+(note the mandatory enclosing brackets),
|
|
|
+where @rep{XXX} is a sequence of one or more hexadecimal digits
|
|
|
+representing the character code point.
|
|
|
+
|
|
|
+Literal strings can also be defined using a long format
|
|
|
+enclosed by @def{long brackets}.
|
|
|
+We define an @def{opening long bracket of level @rep{n}} as an opening
|
|
|
+square bracket followed by @rep{n} equal signs followed by another
|
|
|
+opening square bracket.
|
|
|
+So, an opening long bracket of @N{level 0} is written as @T{[[}, @C{]]}
|
|
|
+an opening long bracket of @N{level 1} is written as @T{[=[}, @C{]]}
|
|
|
+and so on.
|
|
|
+A @emph{closing long bracket} is defined similarly;
|
|
|
+for instance,
|
|
|
+a closing long bracket of @N{level 4} is written as @C{[[} @T{]====]}.
|
|
|
+A @def{long literal} starts with an opening long bracket of any level and
|
|
|
+ends at the first closing long bracket of the same level.
|
|
|
+It can contain any text except a closing bracket of the same level.
|
|
|
+Literals in this bracketed form can run for several lines,
|
|
|
+do not interpret any escape sequences,
|
|
|
+and ignore long brackets of any other level.
|
|
|
+Any kind of end-of-line sequence
|
|
|
+(carriage return, newline, carriage return followed by newline,
|
|
|
+or newline followed by carriage return)
|
|
|
+is converted to a simple newline.
|
|
|
+
|
|
|
+For convenience,
|
|
|
+when the opening long bracket is immediately followed by a newline,
|
|
|
+the newline is not included in the string.
|
|
|
+As an example, in a system using ASCII
|
|
|
+(in which @Char{a} is coded @N{as 97},
|
|
|
+newline is coded @N{as 10}, and @Char{1} is coded @N{as 49}),
|
|
|
+the five literal strings below denote the same string:
|
|
|
+@verbatim{
|
|
|
+a = 'alo\n123"'
|
|
|
+a = "alo\n123\""
|
|
|
+a = '\97lo\10\04923"'
|
|
|
+a = [[alo
|
|
|
+123"]]
|
|
|
+a = [==[
|
|
|
+alo
|
|
|
+123"]==]
|
|
|
+}
|
|
|
+
|
|
|
+Any byte in a literal string not
|
|
|
+explicitly affected by the previous rules represents itself.
|
|
|
+However, Lua opens files for parsing in text mode,
|
|
|
+and the system file functions may have problems with
|
|
|
+some control characters.
|
|
|
+So, it is safer to represent
|
|
|
+non-text data as a quoted literal with
|
|
|
+explicit escape sequences for the non-text characters.
|
|
|
+
|
|
|
+A @def{numeric constant} (or @def{numeral})
|
|
|
+can be written with an optional fractional part
|
|
|
+and an optional decimal exponent,
|
|
|
+marked by a letter @Char{e} or @Char{E}.
|
|
|
+Lua also accepts @x{hexadecimal constants},
|
|
|
+which start with @T{0x} or @T{0X}.
|
|
|
+Hexadecimal constants also accept an optional fractional part
|
|
|
+plus an optional binary exponent,
|
|
|
+marked by a letter @Char{p} or @Char{P}.
|
|
|
+A numeric constant with a radix point or an exponent
|
|
|
+denotes a float;
|
|
|
+otherwise,
|
|
|
+if its value fits in an integer,
|
|
|
+it denotes an integer.
|
|
|
+Examples of valid integer constants are
|
|
|
+@verbatim{
|
|
|
+3 345 0xff 0xBEBADA
|
|
|
+}
|
|
|
+Examples of valid float constants are
|
|
|
+@verbatim{
|
|
|
+3.0 3.1416 314.16e-2 0.31416E1 34e1
|
|
|
+0x0.1E 0xA23p-4 0X1.921FB54442D18P+1
|
|
|
+}
|
|
|
+
|
|
|
+A @def{comment} starts with a double hyphen (@T{--})
|
|
|
+anywhere outside a string.
|
|
|
+If the text immediately after @T{--} is not an opening long bracket,
|
|
|
+the comment is a @def{short comment},
|
|
|
+which runs until the end of the line.
|
|
|
+Otherwise, it is a @def{long comment},
|
|
|
+which runs until the corresponding closing long bracket.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{variables| @title{Variables}
|
|
|
+
|
|
|
+Variables are places that store values.
|
|
|
+There are three kinds of variables in Lua:
|
|
|
+global variables, local variables, and table fields.
|
|
|
+
|
|
|
+A single name can denote a global variable or a local variable
|
|
|
+(or a function's formal parameter,
|
|
|
+which is a particular kind of local variable):
|
|
|
+@Produc{
|
|
|
+@producname{var}@producbody{@bnfNter{Name}}
|
|
|
+}
|
|
|
+@bnfNter{Name} denotes identifiers, as defined in @See{lexical}.
|
|
|
+
|
|
|
+Any variable name is assumed to be global unless explicitly declared
|
|
|
+as a local @see{localvar}.
|
|
|
+@x{Local variables} are @emph{lexically scoped}:
|
|
|
+local variables can be freely accessed by functions
|
|
|
+defined inside their scope @see{visibility}.
|
|
|
+
|
|
|
+Before the first assignment to a variable, its value is @nil.
|
|
|
+
|
|
|
+Square brackets are used to index a table:
|
|
|
+@Produc{
|
|
|
+@producname{var}@producbody{prefixexp @bnfter{[} exp @bnfter{]}}
|
|
|
+}
|
|
|
+The meaning of accesses to table fields can be changed via metatables
|
|
|
+@see{metatable}.
|
|
|
+
|
|
|
+The syntax @id{var.Name} is just syntactic sugar for
|
|
|
+@T{var["Name"]}:
|
|
|
+@Produc{
|
|
|
+@producname{var}@producbody{prefixexp @bnfter{.} @bnfNter{Name}}
|
|
|
+}
|
|
|
+
|
|
|
+An access to a global variable @id{x}
|
|
|
+is equivalent to @id{_ENV.x}.
|
|
|
+Due to the way that chunks are compiled,
|
|
|
+the variable @id{_ENV} itself is never global @see{globalenv}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{stats| @title{Statements}
|
|
|
+
|
|
|
+Lua supports an almost conventional set of @x{statements},
|
|
|
+similar to those in Pascal or C.
|
|
|
+This set includes
|
|
|
+assignments, control structures, function calls,
|
|
|
+and variable declarations.
|
|
|
+
|
|
|
+@sect3{@title{Blocks}
|
|
|
+
|
|
|
+A @x{block} is a list of statements,
|
|
|
+which are executed sequentially:
|
|
|
+@Produc{
|
|
|
+@producname{block}@producbody{@bnfrep{stat}}
|
|
|
+}
|
|
|
+Lua has @def{empty statements}
|
|
|
+that allow you to separate statements with semicolons,
|
|
|
+start a block with a semicolon
|
|
|
+or write two semicolons in sequence:
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@bnfter{;}}
|
|
|
+}
|
|
|
+
|
|
|
+Function calls and assignments
|
|
|
+can start with an open parenthesis.
|
|
|
+This possibility leads to an ambiguity in Lua's grammar.
|
|
|
+Consider the following fragment:
|
|
|
+@verbatim{
|
|
|
+a = b + c
|
|
|
+(print or io.write)('done')
|
|
|
+}
|
|
|
+The grammar could see it in two ways:
|
|
|
+@verbatim{
|
|
|
+a = b + c(print or io.write)('done')
|
|
|
+
|
|
|
+a = b + c; (print or io.write)('done')
|
|
|
+}
|
|
|
+The current parser always sees such constructions
|
|
|
+in the first way,
|
|
|
+interpreting the open parenthesis
|
|
|
+as the start of the arguments to a call.
|
|
|
+To avoid this ambiguity,
|
|
|
+it is a good practice to always precede with a semicolon
|
|
|
+statements that start with a parenthesis:
|
|
|
+@verbatim{
|
|
|
+;(print or io.write)('done')
|
|
|
+}
|
|
|
+
|
|
|
+A block can be explicitly delimited to produce a single statement:
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@Rw{do} block @Rw{end}}
|
|
|
+}
|
|
|
+Explicit blocks are useful
|
|
|
+to control the scope of variable declarations.
|
|
|
+Explicit blocks are also sometimes used to
|
|
|
+add a @Rw{return} statement in the middle
|
|
|
+of another block @see{control}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{chunks| @title{Chunks}
|
|
|
+
|
|
|
+The unit of compilation of Lua is called a @def{chunk}.
|
|
|
+Syntactically,
|
|
|
+a chunk is simply a block:
|
|
|
+@Produc{
|
|
|
+@producname{chunk}@producbody{block}
|
|
|
+}
|
|
|
+
|
|
|
+Lua handles a chunk as the body of an anonymous function
|
|
|
+with a variable number of arguments
|
|
|
+@see{func-def}.
|
|
|
+As such, chunks can define local variables,
|
|
|
+receive arguments, and return values.
|
|
|
+Moreover, such anonymous function is compiled as in the
|
|
|
+scope of an external local variable called @id{_ENV} @see{globalenv}.
|
|
|
+The resulting function always has @id{_ENV} as its only upvalue,
|
|
|
+even if it does not use that variable.
|
|
|
+
|
|
|
+A chunk can be stored in a file or in a string inside the host program.
|
|
|
+To execute a chunk,
|
|
|
+Lua first @emph{loads} it,
|
|
|
+precompiling the chunk's code into instructions for a virtual machine,
|
|
|
+and then Lua executes the compiled code
|
|
|
+with an interpreter for the virtual machine.
|
|
|
+
|
|
|
+Chunks can also be precompiled into binary form;
|
|
|
+see program @idx{luac} and function @Lid{string.dump} for details.
|
|
|
+Programs in source and compiled forms are interchangeable;
|
|
|
+Lua automatically detects the file type and acts accordingly @seeF{load}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{assignment| @title{Assignment}
|
|
|
+
|
|
|
+Lua allows @x{multiple assignments}.
|
|
|
+Therefore, the syntax for assignment
|
|
|
+defines a list of variables on the left side
|
|
|
+and a list of expressions on the right side.
|
|
|
+The elements in both lists are separated by commas:
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{varlist @bnfter{=} explist}
|
|
|
+@producname{varlist}@producbody{var @bnfrep{@bnfter{,} var}}
|
|
|
+@producname{explist}@producbody{exp @bnfrep{@bnfter{,} exp}}
|
|
|
+}
|
|
|
+Expressions are discussed in @See{expressions}.
|
|
|
+
|
|
|
+Before the assignment,
|
|
|
+the list of values is @emph{adjusted} to the length of
|
|
|
+the list of variables.@index{adjustment}
|
|
|
+If there are more values than needed,
|
|
|
+the excess values are thrown away.
|
|
|
+If there are fewer values than needed,
|
|
|
+the list is extended with as many @nil's as needed.
|
|
|
+If the list of expressions ends with a function call,
|
|
|
+then all values returned by that call enter the list of values,
|
|
|
+before the adjustment
|
|
|
+(except when the call is enclosed in parentheses; see @See{expressions}).
|
|
|
+
|
|
|
+The assignment statement first evaluates all its expressions
|
|
|
+and only then the assignments are performed.
|
|
|
+Thus the code
|
|
|
+@verbatim{
|
|
|
+i = 3
|
|
|
+i, a[i] = i+1, 20
|
|
|
+}
|
|
|
+sets @T{a[3]} to 20, without affecting @T{a[4]}
|
|
|
+because the @id{i} in @T{a[i]} is evaluated (to 3)
|
|
|
+before it is @N{assigned 4}.
|
|
|
+Similarly, the line
|
|
|
+@verbatim{
|
|
|
+x, y = y, x
|
|
|
+}
|
|
|
+exchanges the values of @id{x} and @id{y},
|
|
|
+and
|
|
|
+@verbatim{
|
|
|
+x, y, z = y, z, x
|
|
|
+}
|
|
|
+cyclically permutes the values of @id{x}, @id{y}, and @id{z}.
|
|
|
+
|
|
|
+An assignment to a global name @T{x = val}
|
|
|
+is equivalent to the assignment
|
|
|
+@T{_ENV.x = val} @see{globalenv}.
|
|
|
+
|
|
|
+The meaning of assignments to table fields and
|
|
|
+global variables (which are actually table fields, too)
|
|
|
+can be changed via metatables @see{metatable}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{control| @title{Control Structures}
|
|
|
+The control structures
|
|
|
+@Rw{if}, @Rw{while}, and @Rw{repeat} have the usual meaning and
|
|
|
+familiar syntax:
|
|
|
+@index{while-do statement}
|
|
|
+@index{repeat-until statement}
|
|
|
+@index{if-then-else statement}
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@Rw{while} exp @Rw{do} block @Rw{end}}
|
|
|
+@producname{stat}@producbody{@Rw{repeat} block @Rw{until} exp}
|
|
|
+@producname{stat}@producbody{@Rw{if} exp @Rw{then} block
|
|
|
+ @bnfrep{@Rw{elseif} exp @Rw{then} block}
|
|
|
+ @bnfopt{@Rw{else} block} @Rw{end}}
|
|
|
+}
|
|
|
+Lua also has a @Rw{for} statement, in two flavors @see{for}.
|
|
|
+
|
|
|
+The @x{condition expression} of a
|
|
|
+control structure can return any value.
|
|
|
+Both @false and @nil test false.
|
|
|
+All values different from @nil and @false test true.
|
|
|
+(In particular, the number 0 and the empty string also test true).
|
|
|
+
|
|
|
+In the @Rw{repeat}@En@Rw{until} loop,
|
|
|
+the inner block does not end at the @Rw{until} keyword,
|
|
|
+but only after the condition.
|
|
|
+So, the condition can refer to local variables
|
|
|
+declared inside the loop block.
|
|
|
+
|
|
|
+The @Rw{goto} statement transfers the program control to a label.
|
|
|
+For syntactical reasons,
|
|
|
+labels in Lua are considered statements too:
|
|
|
+@index{goto statement}
|
|
|
+@index{label}
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@Rw{goto} Name}
|
|
|
+@producname{stat}@producbody{label}
|
|
|
+@producname{label}@producbody{@bnfter{::} Name @bnfter{::}}
|
|
|
+}
|
|
|
+
|
|
|
+A label is visible in the entire block where it is defined,
|
|
|
+except
|
|
|
+inside nested blocks where a label with the same name is defined and
|
|
|
+inside nested functions.
|
|
|
+A goto may jump to any visible label as long as it does not
|
|
|
+enter into the scope of a local variable.
|
|
|
+
|
|
|
+Labels and empty statements are called @def{void statements},
|
|
|
+as they perform no actions.
|
|
|
+
|
|
|
+The @Rw{break} statement terminates the execution of a
|
|
|
+@Rw{while}, @Rw{repeat}, or @Rw{for} loop,
|
|
|
+skipping to the next statement after the loop:
|
|
|
+@index{break statement}
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@Rw{break}}
|
|
|
+}
|
|
|
+A @Rw{break} ends the innermost enclosing loop.
|
|
|
+
|
|
|
+The @Rw{return} statement is used to return values
|
|
|
+from a function or a chunk
|
|
|
+(which is an anonymous function).
|
|
|
+@index{return statement}
|
|
|
+Functions can return more than one value,
|
|
|
+so the syntax for the @Rw{return} statement is
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@Rw{return} @bnfopt{explist} @bnfopt{@bnfter{;}}}
|
|
|
+}
|
|
|
+
|
|
|
+The @Rw{return} statement can only be written
|
|
|
+as the last statement of a block.
|
|
|
+If it is really necessary to @Rw{return} in the middle of a block,
|
|
|
+then an explicit inner block can be used,
|
|
|
+as in the idiom @T{do return end},
|
|
|
+because now @Rw{return} is the last statement in its (inner) block.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{for| @title{For Statement}
|
|
|
+
|
|
|
+@index{for statement}
|
|
|
+The @Rw{for} statement has two forms:
|
|
|
+one numerical and one generic.
|
|
|
+
|
|
|
+The numerical @Rw{for} loop repeats a block of code while a
|
|
|
+control variable runs through an arithmetic progression.
|
|
|
+It has the following syntax:
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@Rw{for} @bnfNter{Name} @bnfter{=}
|
|
|
+ exp @bnfter{,} exp @bnfopt{@bnfter{,} exp} @Rw{do} block @Rw{end}}
|
|
|
+}
|
|
|
+The @emph{block} is repeated for @emph{name} starting at the value of
|
|
|
+the first @emph{exp}, until it passes the second @emph{exp} by steps of the
|
|
|
+third @emph{exp}.
|
|
|
+More precisely, a @Rw{for} statement like
|
|
|
+@verbatim{
|
|
|
+for v = @rep{e1}, @rep{e2}, @rep{e3} do @rep{block} end
|
|
|
+}
|
|
|
+is equivalent to the code:
|
|
|
+@verbatim{
|
|
|
+do
|
|
|
+ local @rep{var}, @rep{limit}, @rep{step} = tonumber(@rep{e1}), tonumber(@rep{e2}), tonumber(@rep{e3})
|
|
|
+ if not (@rep{var} and @rep{limit} and @rep{step}) then error() end
|
|
|
+ @rep{var} = @rep{var} - @rep{step}
|
|
|
+ while true do
|
|
|
+ @rep{var} = @rep{var} + @rep{step}
|
|
|
+ if (@rep{step} >= 0 and @rep{var} > @rep{limit}) or (@rep{step} < 0 and @rep{var} < @rep{limit}) then
|
|
|
+ break
|
|
|
+ end
|
|
|
+ local v = @rep{var}
|
|
|
+ @rep{block}
|
|
|
+ end
|
|
|
+end
|
|
|
+}
|
|
|
+
|
|
|
+Note the following:
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{
|
|
|
+All three control expressions are evaluated only once,
|
|
|
+before the loop starts.
|
|
|
+They must all result in numbers.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+@T{@rep{var}}, @T{@rep{limit}}, and @T{@rep{step}} are invisible variables.
|
|
|
+The names shown here are for explanatory purposes only.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+If the third expression (the step) is absent,
|
|
|
+then a step @N{of 1} is used.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+You can use @Rw{break} and @Rw{goto} to exit a @Rw{for} loop.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+The loop variable @T{v} is local to the loop body.
|
|
|
+If you need its value after the loop,
|
|
|
+assign it to another variable before exiting the loop.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+The values in @rep{var}, @rep{limit}, and @rep{step}
|
|
|
+can be integers or floats.
|
|
|
+All operations on them respect the usual rules in Lua.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+The generic @Rw{for} statement works over functions,
|
|
|
+called @def{iterators}.
|
|
|
+On each iteration, the iterator function is called to produce a new value,
|
|
|
+stopping when this new value is @nil.
|
|
|
+The generic @Rw{for} loop has the following syntax:
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@Rw{for} namelist @Rw{in} explist
|
|
|
+ @Rw{do} block @Rw{end}}
|
|
|
+@producname{namelist}@producbody{@bnfNter{Name} @bnfrep{@bnfter{,} @bnfNter{Name}}}
|
|
|
+}
|
|
|
+A @Rw{for} statement like
|
|
|
+@verbatim{
|
|
|
+for @rep{var_1}, @Cdots, @rep{var_n} in @rep{explist} do @rep{block} end
|
|
|
+}
|
|
|
+is equivalent to the code:
|
|
|
+@verbatim{
|
|
|
+do
|
|
|
+ local @rep{f}, @rep{s}, @rep{var} = @rep{explist}
|
|
|
+ while true do
|
|
|
+ local @rep{var_1}, @Cdots, @rep{var_n} = @rep{f}(@rep{s}, @rep{var})
|
|
|
+ if @rep{var_1} == nil then break end
|
|
|
+ @rep{var} = @rep{var_1}
|
|
|
+ @rep{block}
|
|
|
+ end
|
|
|
+end
|
|
|
+}
|
|
|
+Note the following:
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{
|
|
|
+@T{@rep{explist}} is evaluated only once.
|
|
|
+Its results are an @emph{iterator} function,
|
|
|
+a @emph{state},
|
|
|
+and an initial value for the first @emph{iterator variable}.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+@T{@rep{f}}, @T{@rep{s}}, and @T{@rep{var}} are invisible variables.
|
|
|
+The names are here for explanatory purposes only.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+You can use @Rw{break} to exit a @Rw{for} loop.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+The loop variables @T{@rep{var_i}} are local to the loop;
|
|
|
+you cannot use their values after the @Rw{for} ends.
|
|
|
+If you need these values,
|
|
|
+then assign them to other variables before breaking or exiting the loop.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{funcstat| @title{Function Calls as Statements}
|
|
|
+To allow possible side-effects,
|
|
|
+function calls can be executed as statements:
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{functioncall}
|
|
|
+}
|
|
|
+In this case, all returned values are thrown away.
|
|
|
+Function calls are explained in @See{functioncall}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{localvar| @title{Local Declarations}
|
|
|
+@x{Local variables} can be declared anywhere inside a block.
|
|
|
+The declaration can include an initial assignment:
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@Rw{local} namelist @bnfopt{@bnfter{=} explist}}
|
|
|
+}
|
|
|
+If present, an initial assignment has the same semantics
|
|
|
+of a multiple assignment @see{assignment}.
|
|
|
+Otherwise, all variables are initialized with @nil.
|
|
|
+
|
|
|
+A chunk is also a block @see{chunks},
|
|
|
+and so local variables can be declared in a chunk outside any explicit block.
|
|
|
+
|
|
|
+The visibility rules for local variables are explained in @See{visibility}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{expressions| @title{Expressions}
|
|
|
+
|
|
|
+The basic expressions in Lua are the following:
|
|
|
+@Produc{
|
|
|
+@producname{exp}@producbody{prefixexp}
|
|
|
+@producname{exp}@producbody{@Rw{nil} @Or @Rw{false} @Or @Rw{true}}
|
|
|
+@producname{exp}@producbody{@bnfNter{Numeral}}
|
|
|
+@producname{exp}@producbody{@bnfNter{LiteralString}}
|
|
|
+@producname{exp}@producbody{functiondef}
|
|
|
+@producname{exp}@producbody{tableconstructor}
|
|
|
+@producname{exp}@producbody{@bnfter{...}}
|
|
|
+@producname{exp}@producbody{exp binop exp}
|
|
|
+@producname{exp}@producbody{unop exp}
|
|
|
+@producname{prefixexp}@producbody{var @Or functioncall @Or
|
|
|
+ @bnfter{(} exp @bnfter{)}}
|
|
|
+}
|
|
|
+
|
|
|
+Numerals and literal strings are explained in @See{lexical};
|
|
|
+variables are explained in @See{variables};
|
|
|
+function definitions are explained in @See{func-def};
|
|
|
+function calls are explained in @See{functioncall};
|
|
|
+table constructors are explained in @See{tableconstructor}.
|
|
|
+Vararg expressions,
|
|
|
+denoted by three dots (@Char{...}), can only be used when
|
|
|
+directly inside a vararg function;
|
|
|
+they are explained in @See{func-def}.
|
|
|
+
|
|
|
+Binary operators comprise arithmetic operators @see{arith},
|
|
|
+bitwise operators @see{bitwise},
|
|
|
+relational operators @see{rel-ops}, logical operators @see{logic},
|
|
|
+and the concatenation operator @see{concat}.
|
|
|
+Unary operators comprise the unary minus @see{arith},
|
|
|
+the unary bitwise NOT @see{bitwise},
|
|
|
+the unary logical @Rw{not} @see{logic},
|
|
|
+and the unary @def{length operator} @see{len-op}.
|
|
|
+
|
|
|
+Both function calls and vararg expressions can result in multiple values.
|
|
|
+If a function call is used as a statement @see{funcstat},
|
|
|
+then its return list is adjusted to zero elements,
|
|
|
+thus discarding all returned values.
|
|
|
+If an expression is used as the last (or the only) element
|
|
|
+of a list of expressions,
|
|
|
+then no adjustment is made
|
|
|
+(unless the expression is enclosed in parentheses).
|
|
|
+In all other contexts,
|
|
|
+Lua adjusts the result list to one element,
|
|
|
+either discarding all values except the first one
|
|
|
+or adding a single @nil if there are no values.
|
|
|
+
|
|
|
+Here are some examples:
|
|
|
+@verbatim{
|
|
|
+f() -- adjusted to 0 results
|
|
|
+g(f(), x) -- f() is adjusted to 1 result
|
|
|
+g(x, f()) -- g gets x plus all results from f()
|
|
|
+a,b,c = f(), x -- f() is adjusted to 1 result (c gets nil)
|
|
|
+a,b = ... -- a gets the first vararg argument, b gets
|
|
|
+ -- the second (both a and b can get nil if there
|
|
|
+ -- is no corresponding vararg argument)
|
|
|
+
|
|
|
+a,b,c = x, f() -- f() is adjusted to 2 results
|
|
|
+a,b,c = f() -- f() is adjusted to 3 results
|
|
|
+return f() -- returns all results from f()
|
|
|
+return ... -- returns all received vararg arguments
|
|
|
+return x,y,f() -- returns x, y, and all results from f()
|
|
|
+{f()} -- creates a list with all results from f()
|
|
|
+{...} -- creates a list with all vararg arguments
|
|
|
+{f(), nil} -- f() is adjusted to 1 result
|
|
|
+}
|
|
|
+
|
|
|
+Any expression enclosed in parentheses always results in only one value.
|
|
|
+Thus,
|
|
|
+@T{(f(x,y,z))} is always a single value,
|
|
|
+even if @id{f} returns several values.
|
|
|
+(The value of @T{(f(x,y,z))} is the first value returned by @id{f}
|
|
|
+or @nil if @id{f} does not return any values.)
|
|
|
+
|
|
|
+
|
|
|
+
|
|
|
+@sect3{arith| @title{Arithmetic Operators}
|
|
|
+Lua supports the following @x{arithmetic operators}:
|
|
|
+@description{
|
|
|
+@item{@T{+}|addition}
|
|
|
+@item{@T{-}|subtraction}
|
|
|
+@item{@T{*}|multiplication}
|
|
|
+@item{@T{/}|float division}
|
|
|
+@item{@T{//}|floor division}
|
|
|
+@item{@T{%}|modulo}
|
|
|
+@item{@T{^}|exponentiation}
|
|
|
+@item{@T{-}|unary minus}
|
|
|
+}
|
|
|
+
|
|
|
+With the exception of exponentiation and float division,
|
|
|
+the arithmetic operators work as follows:
|
|
|
+If both operands are integers,
|
|
|
+the operation is performed over integers and the result is an integer.
|
|
|
+Otherwise, if both operands are numbers,
|
|
|
+then they are converted to floats,
|
|
|
+the operation is performed following the usual rules
|
|
|
+for floating-point arithmetic
|
|
|
+(usually the @x{IEEE 754} standard),
|
|
|
+and the result is a float.
|
|
|
+(The string library coerces strings to numbers in
|
|
|
+arithmetic operations; see @See{coercion} for details.)
|
|
|
+
|
|
|
+Exponentiation and float division (@T{/})
|
|
|
+always convert their operands to floats
|
|
|
+and the result is always a float.
|
|
|
+Exponentiation uses the @ANSI{pow},
|
|
|
+so that it works for non-integer exponents too.
|
|
|
+
|
|
|
+Floor division (@T{//}) is a division
|
|
|
+that rounds the quotient towards minus infinity,
|
|
|
+that is, the floor of the division of its operands.
|
|
|
+
|
|
|
+Modulo is defined as the remainder of a division
|
|
|
+that rounds the quotient towards minus infinity (floor division).
|
|
|
+
|
|
|
+In case of overflows in integer arithmetic,
|
|
|
+all operations @emphx{wrap around},
|
|
|
+according to the usual rules of two-complement arithmetic.
|
|
|
+(In other words,
|
|
|
+they return the unique representable integer
|
|
|
+that is equal modulo @M{2@sp{64}} to the mathematical result.)
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{bitwise| @title{Bitwise Operators}
|
|
|
+Lua supports the following @x{bitwise operators}:
|
|
|
+@description{
|
|
|
+@item{@T{&}|bitwise AND}
|
|
|
+@item{@T{@VerBar}|bitwise OR}
|
|
|
+@item{@T{~}|bitwise exclusive OR}
|
|
|
+@item{@T{>>}|right shift}
|
|
|
+@item{@T{<<}|left shift}
|
|
|
+@item{@T{~}|unary bitwise NOT}
|
|
|
+}
|
|
|
+
|
|
|
+All bitwise operations convert its operands to integers
|
|
|
+@see{coercion},
|
|
|
+operate on all bits of those integers,
|
|
|
+and result in an integer.
|
|
|
+
|
|
|
+Both right and left shifts fill the vacant bits with zeros.
|
|
|
+Negative displacements shift to the other direction;
|
|
|
+displacements with absolute values equal to or higher than
|
|
|
+the number of bits in an integer
|
|
|
+result in zero (as all bits are shifted out).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{coercion| @title{Coercions and Conversions}
|
|
|
+Lua provides some automatic conversions between some
|
|
|
+types and representations at run time.
|
|
|
+Bitwise operators always convert float operands to integers.
|
|
|
+Exponentiation and float division
|
|
|
+always convert integer operands to floats.
|
|
|
+All other arithmetic operations applied to mixed numbers
|
|
|
+(integers and floats) convert the integer operand to a float.
|
|
|
+The C API also converts both integers to floats and
|
|
|
+floats to integers, as needed.
|
|
|
+Moreover, string concatenation accepts numbers as arguments,
|
|
|
+besides strings.
|
|
|
+
|
|
|
+In a conversion from integer to float,
|
|
|
+if the integer value has an exact representation as a float,
|
|
|
+that is the result.
|
|
|
+Otherwise,
|
|
|
+the conversion gets the nearest higher or
|
|
|
+the nearest lower representable value.
|
|
|
+This kind of conversion never fails.
|
|
|
+
|
|
|
+The conversion from float to integer
|
|
|
+checks whether the float has an exact representation as an integer
|
|
|
+(that is, the float has an integral value and
|
|
|
+it is in the range of integer representation).
|
|
|
+If it does, that representation is the result.
|
|
|
+Otherwise, the conversion fails.
|
|
|
+
|
|
|
+The string library uses metamethods that try to coerce
|
|
|
+strings to numbers in all arithmetic operations.
|
|
|
+Any string operator is converted to an integer or a float,
|
|
|
+following its syntax and the rules of the Lua lexer.
|
|
|
+(The string may have also leading and trailing spaces and a sign.)
|
|
|
+All conversions from strings to numbers
|
|
|
+accept both a dot and the current locale mark
|
|
|
+as the radix character.
|
|
|
+(The Lua lexer, however, accepts only a dot.)
|
|
|
+
|
|
|
+The conversion from numbers to strings uses a
|
|
|
+non-specified human-readable format.
|
|
|
+For complete control over how numbers are converted to strings,
|
|
|
+use the @id{format} function from the string library
|
|
|
+@seeF{string.format}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{rel-ops| @title{Relational Operators}
|
|
|
+Lua supports the following @x{relational operators}:
|
|
|
+@description{
|
|
|
+@item{@T{==}|equality}
|
|
|
+@item{@T{~=}|inequality}
|
|
|
+@item{@T{<}|less than}
|
|
|
+@item{@T{>}|greater than}
|
|
|
+@item{@T{<=}|less or equal}
|
|
|
+@item{@T{>=}|greater or equal}
|
|
|
+}
|
|
|
+These operators always result in @false or @true.
|
|
|
+
|
|
|
+Equality (@T{==}) first compares the type of its operands.
|
|
|
+If the types are different, then the result is @false.
|
|
|
+Otherwise, the values of the operands are compared.
|
|
|
+Strings are compared in the obvious way.
|
|
|
+Numbers are equal if they denote the same mathematical value.
|
|
|
+
|
|
|
+Tables, userdata, and threads
|
|
|
+are compared by reference:
|
|
|
+two objects are considered equal only if they are the same object.
|
|
|
+Every time you create a new object
|
|
|
+(a table, userdata, or thread),
|
|
|
+this new object is different from any previously existing object.
|
|
|
+A closure is always equal to itself.
|
|
|
+Closures with any detectable difference
|
|
|
+(different behavior, different definition) are always different.
|
|
|
+Closures created at different times but with no detectable differences
|
|
|
+may be classified as equal or not
|
|
|
+(depending on internal cashing details).
|
|
|
+
|
|
|
+You can change the way that Lua compares tables and userdata
|
|
|
+by using the @idx{__eq} metamethod @see{metatable}.
|
|
|
+
|
|
|
+Equality comparisons do not convert strings to numbers
|
|
|
+or vice versa.
|
|
|
+Thus, @T{"0"==0} evaluates to @false,
|
|
|
+and @T{t[0]} and @T{t["0"]} denote different
|
|
|
+entries in a table.
|
|
|
+
|
|
|
+The operator @T{~=} is exactly the negation of equality (@T{==}).
|
|
|
+
|
|
|
+The order operators work as follows.
|
|
|
+If both arguments are numbers,
|
|
|
+then they are compared according to their mathematical values
|
|
|
+(regardless of their subtypes).
|
|
|
+Otherwise, if both arguments are strings,
|
|
|
+then their values are compared according to the current locale.
|
|
|
+Otherwise, Lua tries to call the @idx{__lt} or the @idx{__le}
|
|
|
+metamethod @see{metatable}.
|
|
|
+A comparison @T{a > b} is translated to @T{b < a}
|
|
|
+and @T{a >= b} is translated to @T{b <= a}.
|
|
|
+
|
|
|
+Following the @x{IEEE 754} standard,
|
|
|
+@x{NaN} is considered neither smaller than,
|
|
|
+nor equal to, nor greater than any value (including itself).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{logic| @title{Logical Operators}
|
|
|
+The @x{logical operators} in Lua are
|
|
|
+@Rw{and}, @Rw{or}, and @Rw{not}.
|
|
|
+Like the control structures @see{control},
|
|
|
+all logical operators consider both @false and @nil as false
|
|
|
+and anything else as true.
|
|
|
+
|
|
|
+The negation operator @Rw{not} always returns @false or @true.
|
|
|
+The conjunction operator @Rw{and} returns its first argument
|
|
|
+if this value is @false or @nil;
|
|
|
+otherwise, @Rw{and} returns its second argument.
|
|
|
+The disjunction operator @Rw{or} returns its first argument
|
|
|
+if this value is different from @nil and @false;
|
|
|
+otherwise, @Rw{or} returns its second argument.
|
|
|
+Both @Rw{and} and @Rw{or} use @x{short-circuit evaluation};
|
|
|
+that is,
|
|
|
+the second operand is evaluated only if necessary.
|
|
|
+Here are some examples:
|
|
|
+@verbatim{
|
|
|
+10 or 20 --> 10
|
|
|
+10 or error() --> 10
|
|
|
+nil or "a" --> "a"
|
|
|
+nil and 10 --> nil
|
|
|
+false and error() --> false
|
|
|
+false and nil --> false
|
|
|
+false or nil --> nil
|
|
|
+10 and 20 --> 20
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{concat| @title{Concatenation}
|
|
|
+The string @x{concatenation} operator in Lua is
|
|
|
+denoted by two dots (@Char{..}).
|
|
|
+If both operands are strings or numbers, then they are converted to
|
|
|
+strings according to the rules described in @See{coercion}.
|
|
|
+Otherwise, the @idx{__concat} metamethod is called @see{metatable}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{len-op| @title{The Length Operator}
|
|
|
+
|
|
|
+The length operator is denoted by the unary prefix operator @T{#}.
|
|
|
+
|
|
|
+The length of a string is its number of bytes
|
|
|
+(that is, the usual meaning of string length when each
|
|
|
+character is one byte).
|
|
|
+
|
|
|
+The length operator applied on a table
|
|
|
+returns a @x{border} in that table.
|
|
|
+A @def{border} in a table @id{t} is any natural number
|
|
|
+that satisfies the following condition:
|
|
|
+@verbatim{
|
|
|
+(border == 0 or t[border] ~= nil) and t[border + 1] == nil
|
|
|
+}
|
|
|
+In words,
|
|
|
+a border is any (natural) index present in the table
|
|
|
+that is followed by an absent index
|
|
|
+(or zero, when index 1 is absent).
|
|
|
+
|
|
|
+A table with exactly one border is called a @def{sequence}.
|
|
|
+For instance, the table @T{{10, 20, 30, 40, 50}} is a sequence,
|
|
|
+as it has only one border (5).
|
|
|
+The table @T{{10, 20, 30, nil, 50}} has two borders (3 and 5),
|
|
|
+and therefore it is not a sequence.
|
|
|
+The table @T{{nil, 20, 30, nil, nil, 60, nil}}
|
|
|
+has three borders (0, 3, and 6),
|
|
|
+so it is not a sequence, too.
|
|
|
+The table @T{{}} is a sequence with border 0.
|
|
|
+Note that non-natural keys do not interfere
|
|
|
+with whether a table is a sequence.
|
|
|
+
|
|
|
+When @id{t} is a sequence,
|
|
|
+@T{#t} returns its only border,
|
|
|
+which corresponds to the intuitive notion of the length of the sequence.
|
|
|
+When @id{t} is not a sequence,
|
|
|
+@T{#t} can return any of its borders.
|
|
|
+(The exact one depends on details of
|
|
|
+the internal representation of the table,
|
|
|
+which in turn can depend on how the table was populated and
|
|
|
+the memory addresses of its non-numeric keys.)
|
|
|
+
|
|
|
+The computation of the length of a table
|
|
|
+has a guaranteed worst time of @M{O(log n)},
|
|
|
+where @M{n} is the largest natural key in the table.
|
|
|
+
|
|
|
+A program can modify the behavior of the length operator for
|
|
|
+any value but strings through the @idx{__len} metamethod @see{metatable}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{prec| @title{Precedence}
|
|
|
+@x{Operator precedence} in Lua follows the table below,
|
|
|
+from lower to higher priority:
|
|
|
+@verbatim{
|
|
|
+or
|
|
|
+and
|
|
|
+< > <= >= ~= ==
|
|
|
+|
|
|
|
+~
|
|
|
+&
|
|
|
+<< >>
|
|
|
+..
|
|
|
++ -
|
|
|
+* / // %
|
|
|
+unary operators (not # - ~)
|
|
|
+^
|
|
|
+}
|
|
|
+As usual,
|
|
|
+you can use parentheses to change the precedences of an expression.
|
|
|
+The concatenation (@Char{..}) and exponentiation (@Char{^})
|
|
|
+operators are right associative.
|
|
|
+All other binary operators are left associative.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{tableconstructor| @title{Table Constructors}
|
|
|
+Table @x{constructors} are expressions that create tables.
|
|
|
+Every time a constructor is evaluated, a new table is created.
|
|
|
+A constructor can be used to create an empty table
|
|
|
+or to create a table and initialize some of its fields.
|
|
|
+The general syntax for constructors is
|
|
|
+@Produc{
|
|
|
+@producname{tableconstructor}@producbody{@bnfter{@Open} @bnfopt{fieldlist} @bnfter{@Close}}
|
|
|
+@producname{fieldlist}@producbody{field @bnfrep{fieldsep field} @bnfopt{fieldsep}}
|
|
|
+@producname{field}@producbody{@bnfter{[} exp @bnfter{]} @bnfter{=} exp @Or
|
|
|
+ @bnfNter{Name} @bnfter{=} exp @Or exp}
|
|
|
+@producname{fieldsep}@producbody{@bnfter{,} @Or @bnfter{;}}
|
|
|
+}
|
|
|
+
|
|
|
+Each field of the form @T{[exp1] = exp2} adds to the new table an entry
|
|
|
+with key @id{exp1} and value @id{exp2}.
|
|
|
+A field of the form @T{name = exp} is equivalent to
|
|
|
+@T{["name"] = exp}.
|
|
|
+Finally, fields of the form @id{exp} are equivalent to
|
|
|
+@T{[i] = exp}, where @id{i} are consecutive integers
|
|
|
+starting with 1.
|
|
|
+Fields in the other formats do not affect this counting.
|
|
|
+For example,
|
|
|
+@verbatim{
|
|
|
+a = { [f(1)] = g; "x", "y"; x = 1, f(x), [30] = 23; 45 }
|
|
|
+}
|
|
|
+is equivalent to
|
|
|
+@verbatim{
|
|
|
+do
|
|
|
+ local t = {}
|
|
|
+ t[f(1)] = g
|
|
|
+ t[1] = "x" -- 1st exp
|
|
|
+ t[2] = "y" -- 2nd exp
|
|
|
+ t.x = 1 -- t["x"] = 1
|
|
|
+ t[3] = f(x) -- 3rd exp
|
|
|
+ t[30] = 23
|
|
|
+ t[4] = 45 -- 4th exp
|
|
|
+ a = t
|
|
|
+end
|
|
|
+}
|
|
|
+
|
|
|
+The order of the assignments in a constructor is undefined.
|
|
|
+(This order would be relevant only when there are repeated keys.)
|
|
|
+
|
|
|
+If the last field in the list has the form @id{exp}
|
|
|
+and the expression is a function call or a vararg expression,
|
|
|
+then all values returned by this expression enter the list consecutively
|
|
|
+@see{functioncall}.
|
|
|
+
|
|
|
+The field list can have an optional trailing separator,
|
|
|
+as a convenience for machine-generated code.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{functioncall| @title{Function Calls}
|
|
|
+A @x{function call} in Lua has the following syntax:
|
|
|
+@Produc{
|
|
|
+@producname{functioncall}@producbody{prefixexp args}
|
|
|
+}
|
|
|
+In a function call,
|
|
|
+first @bnfNter{prefixexp} and @bnfNter{args} are evaluated.
|
|
|
+If the value of @bnfNter{prefixexp} has type @emph{function},
|
|
|
+then this function is called
|
|
|
+with the given arguments.
|
|
|
+Otherwise, the @bnfNter{prefixexp} @idx{__call} metamethod is called,
|
|
|
+having as first argument the value of @bnfNter{prefixexp},
|
|
|
+followed by the original call arguments
|
|
|
+@see{metatable}.
|
|
|
+
|
|
|
+The form
|
|
|
+@Produc{
|
|
|
+@producname{functioncall}@producbody{prefixexp @bnfter{:} @bnfNter{Name} args}
|
|
|
+}
|
|
|
+can be used to call @Q{methods}.
|
|
|
+A call @T{v:name(@rep{args})}
|
|
|
+is syntactic sugar for @T{v.name(v,@rep{args})},
|
|
|
+except that @id{v} is evaluated only once.
|
|
|
+
|
|
|
+Arguments have the following syntax:
|
|
|
+@Produc{
|
|
|
+@producname{args}@producbody{@bnfter{(} @bnfopt{explist} @bnfter{)}}
|
|
|
+@producname{args}@producbody{tableconstructor}
|
|
|
+@producname{args}@producbody{@bnfNter{LiteralString}}
|
|
|
+}
|
|
|
+All argument expressions are evaluated before the call.
|
|
|
+A call of the form @T{f{@rep{fields}}} is
|
|
|
+syntactic sugar for @T{f({@rep{fields}})};
|
|
|
+that is, the argument list is a single new table.
|
|
|
+A call of the form @T{f'@rep{string}'}
|
|
|
+(or @T{f"@rep{string}"} or @T{f[[@rep{string}]]})
|
|
|
+is syntactic sugar for @T{f('@rep{string}')};
|
|
|
+that is, the argument list is a single literal string.
|
|
|
+
|
|
|
+A call of the form @T{return @rep{functioncall}} is called
|
|
|
+a @def{tail call}.
|
|
|
+Lua implements @def{proper tail calls}
|
|
|
+(or @emph{proper tail recursion}):
|
|
|
+in a tail call,
|
|
|
+the called function reuses the stack entry of the calling function.
|
|
|
+Therefore, there is no limit on the number of nested tail calls that
|
|
|
+a program can execute.
|
|
|
+However, a tail call erases any debug information about the
|
|
|
+calling function.
|
|
|
+Note that a tail call only happens with a particular syntax,
|
|
|
+where the @Rw{return} has one single function call as argument;
|
|
|
+this syntax makes the calling function return exactly
|
|
|
+the returns of the called function.
|
|
|
+So, none of the following examples are tail calls:
|
|
|
+@verbatim{
|
|
|
+return (f(x)) -- results adjusted to 1
|
|
|
+return 2 * f(x)
|
|
|
+return x, f(x) -- additional results
|
|
|
+f(x); return -- results discarded
|
|
|
+return x or f(x) -- results adjusted to 1
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{func-def| @title{Function Definitions}
|
|
|
+
|
|
|
+The syntax for function definition is
|
|
|
+@Produc{
|
|
|
+@producname{functiondef}@producbody{@Rw{function} funcbody}
|
|
|
+@producname{funcbody}@producbody{@bnfter{(} @bnfopt{parlist} @bnfter{)} block @Rw{end}}
|
|
|
+}
|
|
|
+
|
|
|
+The following syntactic sugar simplifies function definitions:
|
|
|
+@Produc{
|
|
|
+@producname{stat}@producbody{@Rw{function} funcname funcbody}
|
|
|
+@producname{stat}@producbody{@Rw{local} @Rw{function} @bnfNter{Name} funcbody}
|
|
|
+@producname{funcname}@producbody{@bnfNter{Name} @bnfrep{@bnfter{.} @bnfNter{Name}} @bnfopt{@bnfter{:} @bnfNter{Name}}}
|
|
|
+}
|
|
|
+The statement
|
|
|
+@verbatim{
|
|
|
+function f () @rep{body} end
|
|
|
+}
|
|
|
+translates to
|
|
|
+@verbatim{
|
|
|
+f = function () @rep{body} end
|
|
|
+}
|
|
|
+The statement
|
|
|
+@verbatim{
|
|
|
+function t.a.b.c.f () @rep{body} end
|
|
|
+}
|
|
|
+translates to
|
|
|
+@verbatim{
|
|
|
+t.a.b.c.f = function () @rep{body} end
|
|
|
+}
|
|
|
+The statement
|
|
|
+@verbatim{
|
|
|
+local function f () @rep{body} end
|
|
|
+}
|
|
|
+translates to
|
|
|
+@verbatim{
|
|
|
+local f; f = function () @rep{body} end
|
|
|
+}
|
|
|
+not to
|
|
|
+@verbatim{
|
|
|
+local f = function () @rep{body} end
|
|
|
+}
|
|
|
+(This only makes a difference when the body of the function
|
|
|
+contains references to @id{f}.)
|
|
|
+
|
|
|
+A function definition is an executable expression,
|
|
|
+whose value has type @emph{function}.
|
|
|
+When Lua precompiles a chunk,
|
|
|
+all its function bodies are precompiled too.
|
|
|
+Then, whenever Lua executes the function definition,
|
|
|
+the function is @emph{instantiated} (or @emph{closed}).
|
|
|
+This function instance (or @emphx{closure})
|
|
|
+is the final value of the expression.
|
|
|
+
|
|
|
+Parameters act as local variables that are
|
|
|
+initialized with the argument values:
|
|
|
+@Produc{
|
|
|
+@producname{parlist}@producbody{namelist @bnfopt{@bnfter{,} @bnfter{...}} @Or
|
|
|
+ @bnfter{...}}
|
|
|
+}
|
|
|
+When a Lua function is called,
|
|
|
+it adjusts its list of @x{arguments} to
|
|
|
+the length of its list of parameters,
|
|
|
+unless the function is a @def{vararg function},
|
|
|
+which is indicated by three dots (@Char{...})
|
|
|
+at the end of its parameter list.
|
|
|
+A vararg function does not adjust its argument list;
|
|
|
+instead, it collects all extra arguments and supplies them
|
|
|
+to the function through a @def{vararg expression},
|
|
|
+which is also written as three dots.
|
|
|
+The value of this expression is a list of all actual extra arguments,
|
|
|
+similar to a function with multiple results.
|
|
|
+If a vararg expression is used inside another expression
|
|
|
+or in the middle of a list of expressions,
|
|
|
+then its return list is adjusted to one element.
|
|
|
+If the expression is used as the last element of a list of expressions,
|
|
|
+then no adjustment is made
|
|
|
+(unless that last expression is enclosed in parentheses).
|
|
|
+
|
|
|
+
|
|
|
+As an example, consider the following definitions:
|
|
|
+@verbatim{
|
|
|
+function f(a, b) end
|
|
|
+function g(a, b, ...) end
|
|
|
+function r() return 1,2,3 end
|
|
|
+}
|
|
|
+Then, we have the following mapping from arguments to parameters and
|
|
|
+to the vararg expression:
|
|
|
+@verbatim{
|
|
|
+CALL PARAMETERS
|
|
|
+
|
|
|
+f(3) a=3, b=nil
|
|
|
+f(3, 4) a=3, b=4
|
|
|
+f(3, 4, 5) a=3, b=4
|
|
|
+f(r(), 10) a=1, b=10
|
|
|
+f(r()) a=1, b=2
|
|
|
+
|
|
|
+g(3) a=3, b=nil, ... --> (nothing)
|
|
|
+g(3, 4) a=3, b=4, ... --> (nothing)
|
|
|
+g(3, 4, 5, 8) a=3, b=4, ... --> 5 8
|
|
|
+g(5, r()) a=5, b=1, ... --> 2 3
|
|
|
+}
|
|
|
+
|
|
|
+Results are returned using the @Rw{return} statement @see{control}.
|
|
|
+If control reaches the end of a function
|
|
|
+without encountering a @Rw{return} statement,
|
|
|
+then the function returns with no results.
|
|
|
+
|
|
|
+@index{multiple return}
|
|
|
+There is a system-dependent limit on the number of values
|
|
|
+that a function may return.
|
|
|
+This limit is guaranteed to be larger than 1000.
|
|
|
+
|
|
|
+The @emphx{colon} syntax
|
|
|
+is used for defining @def{methods},
|
|
|
+that is, functions that have an implicit extra parameter @idx{self}.
|
|
|
+Thus, the statement
|
|
|
+@verbatim{
|
|
|
+function t.a.b.c:f (@rep{params}) @rep{body} end
|
|
|
+}
|
|
|
+is syntactic sugar for
|
|
|
+@verbatim{
|
|
|
+t.a.b.c.f = function (self, @rep{params}) @rep{body} end
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{visibility| @title{Visibility Rules}
|
|
|
+
|
|
|
+@index{visibility}
|
|
|
+Lua is a lexically scoped language.
|
|
|
+The scope of a local variable begins at the first statement after
|
|
|
+its declaration and lasts until the last non-void statement
|
|
|
+of the innermost block that includes the declaration.
|
|
|
+Consider the following example:
|
|
|
+@verbatim{
|
|
|
+x = 10 -- global variable
|
|
|
+do -- new block
|
|
|
+ local x = x -- new 'x', with value 10
|
|
|
+ print(x) --> 10
|
|
|
+ x = x+1
|
|
|
+ do -- another block
|
|
|
+ local x = x+1 -- another 'x'
|
|
|
+ print(x) --> 12
|
|
|
+ end
|
|
|
+ print(x) --> 11
|
|
|
+end
|
|
|
+print(x) --> 10 (the global one)
|
|
|
+}
|
|
|
+
|
|
|
+Notice that, in a declaration like @T{local x = x},
|
|
|
+the new @id{x} being declared is not in scope yet,
|
|
|
+and so the second @id{x} refers to the outside variable.
|
|
|
+
|
|
|
+Because of the @x{lexical scoping} rules,
|
|
|
+local variables can be freely accessed by functions
|
|
|
+defined inside their scope.
|
|
|
+A local variable used by an inner function is called
|
|
|
+an @def{upvalue}, or @emphx{external local variable},
|
|
|
+inside the inner function.
|
|
|
+
|
|
|
+Notice that each execution of a @Rw{local} statement
|
|
|
+defines new local variables.
|
|
|
+Consider the following example:
|
|
|
+@verbatim{
|
|
|
+a = {}
|
|
|
+local x = 20
|
|
|
+for i=1,10 do
|
|
|
+ local y = 0
|
|
|
+ a[i] = function () y=y+1; return x+y end
|
|
|
+end
|
|
|
+}
|
|
|
+The loop creates ten closures
|
|
|
+(that is, ten instances of the anonymous function).
|
|
|
+Each of these closures uses a different @id{y} variable,
|
|
|
+while all of them share the same @id{x}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@C{-------------------------------------------------------------------------}
|
|
|
+@sect1{API| @title{The Application Program Interface}
|
|
|
+
|
|
|
+@index{C API}
|
|
|
+This section describes the @N{C API} for Lua, that is,
|
|
|
+the set of @N{C functions} available to the host program to communicate
|
|
|
+with Lua.
|
|
|
+All API functions and related types and constants
|
|
|
+are declared in the header file @defid{lua.h}.
|
|
|
+
|
|
|
+Even when we use the term @Q{function},
|
|
|
+any facility in the API may be provided as a macro instead.
|
|
|
+Except where stated otherwise,
|
|
|
+all such macros use each of their arguments exactly once
|
|
|
+(except for the first argument, which is always a Lua state),
|
|
|
+and so do not generate any hidden side-effects.
|
|
|
+
|
|
|
+As in most @N{C libraries},
|
|
|
+the Lua API functions do not check their arguments
|
|
|
+for validity or consistency.
|
|
|
+However, you can change this behavior by compiling Lua
|
|
|
+with the macro @defid{LUA_USE_APICHECK} defined.
|
|
|
+
|
|
|
+The Lua library is fully reentrant:
|
|
|
+it has no global variables.
|
|
|
+It keeps all information it needs in a dynamic structure,
|
|
|
+called the @def{Lua state}.
|
|
|
+
|
|
|
+Each Lua state has one or more threads,
|
|
|
+which correspond to independent, cooperative lines of execution.
|
|
|
+The type @Lid{lua_State} (despite its name) refers to a thread.
|
|
|
+(Indirectly, through the thread, it also refers to the
|
|
|
+Lua state associated to the thread.)
|
|
|
+
|
|
|
+A pointer to a thread must be passed as the first argument to
|
|
|
+every function in the library, except to @Lid{lua_newstate},
|
|
|
+which creates a Lua state from scratch and returns a pointer
|
|
|
+to the @emph{main thread} in the new state.
|
|
|
+
|
|
|
+
|
|
|
+@sect2{@title{The Stack}
|
|
|
+
|
|
|
+Lua uses a @emph{virtual stack} to pass values to and from C.
|
|
|
+Each element in this stack represents a Lua value
|
|
|
+(@nil, number, string, etc.).
|
|
|
+Functions in the API can access this stack through the
|
|
|
+Lua state parameter that they receive.
|
|
|
+
|
|
|
+Whenever Lua calls C, the called function gets a new stack,
|
|
|
+which is independent of previous stacks and of stacks of
|
|
|
+@N{C functions} that are still active.
|
|
|
+This stack initially contains any arguments to the @N{C function}
|
|
|
+and it is where the @N{C function} can store temporary
|
|
|
+Lua values and must push its results
|
|
|
+to be returned to the caller @seeC{lua_CFunction}.
|
|
|
+
|
|
|
+For convenience,
|
|
|
+most query operations in the API do not follow a strict stack discipline.
|
|
|
+Instead, they can refer to any element in the stack
|
|
|
+by using an @emph{index}:@index{index (API stack)}
|
|
|
+A positive index represents an absolute stack position
|
|
|
+(starting @N{at 1});
|
|
|
+a negative index represents an offset relative to the top of the stack.
|
|
|
+More specifically, if the stack has @rep{n} elements,
|
|
|
+then @N{index 1} represents the first element
|
|
|
+(that is, the element that was pushed onto the stack first)
|
|
|
+and
|
|
|
+@N{index @rep{n}} represents the last element;
|
|
|
+@N{index @num{-1}} also represents the last element
|
|
|
+(that is, the element at @N{the top})
|
|
|
+and index @M{-n} represents the first element.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{stacksize| @title{Stack Size}
|
|
|
+
|
|
|
+When you interact with the Lua API,
|
|
|
+you are responsible for ensuring consistency.
|
|
|
+In particular,
|
|
|
+@emph{you are responsible for controlling stack overflow}.
|
|
|
+You can use the function @Lid{lua_checkstack}
|
|
|
+to ensure that the stack has enough space for pushing new elements.
|
|
|
+
|
|
|
+Whenever Lua calls C,
|
|
|
+it ensures that the stack has space for
|
|
|
+at least @defid{LUA_MINSTACK} extra slots.
|
|
|
+@id{LUA_MINSTACK} is defined as 20,
|
|
|
+so that usually you do not have to worry about stack space
|
|
|
+unless your code has loops pushing elements onto the stack.
|
|
|
+
|
|
|
+When you call a Lua function
|
|
|
+without a fixed number of results @seeF{lua_call},
|
|
|
+Lua ensures that the stack has enough space for all results,
|
|
|
+but it does not ensure any extra space.
|
|
|
+So, before pushing anything in the stack after such a call
|
|
|
+you should use @Lid{lua_checkstack}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{@title{Valid and Acceptable Indices}
|
|
|
+
|
|
|
+Any function in the API that receives stack indices
|
|
|
+works only with @emphx{valid indices} or @emphx{acceptable indices}.
|
|
|
+
|
|
|
+A @def{valid index} is an index that refers to a
|
|
|
+position that stores a modifiable Lua value.
|
|
|
+It comprises stack indices @N{between 1} and the stack top
|
|
|
+(@T{1 @leq abs(index) @leq top})
|
|
|
+@index{stack index}
|
|
|
+plus @def{pseudo-indices},
|
|
|
+which represent some positions that are accessible to @N{C code}
|
|
|
+but that are not in the stack.
|
|
|
+Pseudo-indices are used to access the registry @see{registry}
|
|
|
+and the upvalues of a @N{C function} @see{c-closure}.
|
|
|
+
|
|
|
+Functions that do not need a specific mutable position,
|
|
|
+but only a value (e.g., query functions),
|
|
|
+can be called with acceptable indices.
|
|
|
+An @def{acceptable index} can be any valid index,
|
|
|
+but it also can be any positive index after the stack top
|
|
|
+within the space allocated for the stack,
|
|
|
+that is, indices up to the stack size.
|
|
|
+(Note that 0 is never an acceptable index.)
|
|
|
+Indices to upvalues @see{c-closure} larger than the real number
|
|
|
+of upvalues in the current @N{C function} are also acceptable (but invalid).
|
|
|
+Except when noted otherwise,
|
|
|
+functions in the API work with acceptable indices.
|
|
|
+
|
|
|
+Acceptable indices serve to avoid extra tests
|
|
|
+against the stack top when querying the stack.
|
|
|
+For instance, a @N{C function} can query its third argument
|
|
|
+without the need to first check whether there is a third argument,
|
|
|
+that is, without the need to check whether 3 is a valid index.
|
|
|
+
|
|
|
+For functions that can be called with acceptable indices,
|
|
|
+any non-valid index is treated as if it
|
|
|
+contains a value of a virtual type @defid{LUA_TNONE},
|
|
|
+which behaves like a nil value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{c-closure| @title{C Closures}
|
|
|
+
|
|
|
+When a @N{C function} is created,
|
|
|
+it is possible to associate some values with it,
|
|
|
+thus creating a @def{@N{C closure}}
|
|
|
+@seeC{lua_pushcclosure};
|
|
|
+these values are called @def{upvalues} and are
|
|
|
+accessible to the function whenever it is called.
|
|
|
+
|
|
|
+Whenever a @N{C function} is called,
|
|
|
+its upvalues are located at specific pseudo-indices.
|
|
|
+These pseudo-indices are produced by the macro
|
|
|
+@Lid{lua_upvalueindex}.
|
|
|
+The first upvalue associated with a function is at index
|
|
|
+@T{lua_upvalueindex(1)}, and so on.
|
|
|
+Any access to @T{lua_upvalueindex(@rep{n})},
|
|
|
+where @rep{n} is greater than the number of upvalues of the
|
|
|
+current function
|
|
|
+(but not greater than 256,
|
|
|
+which is one plus the maximum number of upvalues in a closure),
|
|
|
+produces an acceptable but invalid index.
|
|
|
+
|
|
|
+A @N{C closure} can also change the values of its corresponding upvalues.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{registry| @title{Registry}
|
|
|
+
|
|
|
+Lua provides a @def{registry},
|
|
|
+a predefined table that can be used by any @N{C code} to
|
|
|
+store whatever Lua values it needs to store.
|
|
|
+The registry table is always located at pseudo-index
|
|
|
+@defid{LUA_REGISTRYINDEX}.
|
|
|
+Any @N{C library} can store data into this table,
|
|
|
+but it must take care to choose keys
|
|
|
+that are different from those used
|
|
|
+by other libraries, to avoid collisions.
|
|
|
+Typically, you should use as key a string containing your library name,
|
|
|
+or a light userdata with the address of a @N{C object} in your code,
|
|
|
+or any Lua object created by your code.
|
|
|
+As with variable names,
|
|
|
+string keys starting with an underscore followed by
|
|
|
+uppercase letters are reserved for Lua.
|
|
|
+
|
|
|
+The integer keys in the registry are used
|
|
|
+by the reference mechanism @seeC{luaL_ref}
|
|
|
+and by some predefined values.
|
|
|
+Therefore, integer keys must not be used for other purposes.
|
|
|
+
|
|
|
+When you create a new Lua state,
|
|
|
+its registry comes with some predefined values.
|
|
|
+These predefined values are indexed with integer keys
|
|
|
+defined as constants in @id{lua.h}.
|
|
|
+The following constants are defined:
|
|
|
+@description{
|
|
|
+@item{@defid{LUA_RIDX_MAINTHREAD}| At this index the registry has
|
|
|
+the main thread of the state.
|
|
|
+(The main thread is the one created together with the state.)
|
|
|
+}
|
|
|
+
|
|
|
+@item{@defid{LUA_RIDX_GLOBALS}| At this index the registry has
|
|
|
+the @x{global environment}.
|
|
|
+}
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{C-error|@title{Error Handling in C}
|
|
|
+
|
|
|
+Internally, Lua uses the C @id{longjmp} facility to handle errors.
|
|
|
+(Lua will use exceptions if you compile it as C++;
|
|
|
+search for @id{LUAI_THROW} in the source code for details.)
|
|
|
+When Lua faces any error
|
|
|
+(such as a @x{memory allocation error} or a type error)
|
|
|
+it @emph{raises} an error;
|
|
|
+that is, it does a long jump.
|
|
|
+A @emphx{protected environment} uses @id{setjmp}
|
|
|
+to set a recovery point;
|
|
|
+any error jumps to the most recent active recovery point.
|
|
|
+
|
|
|
+Inside a @N{C function} you can raise an error by calling @Lid{lua_error}.
|
|
|
+
|
|
|
+Most functions in the API can raise an error,
|
|
|
+for instance due to a @x{memory allocation error}.
|
|
|
+The documentation for each function indicates whether
|
|
|
+it can raise errors.
|
|
|
+
|
|
|
+If an error happens outside any protected environment,
|
|
|
+Lua calls a @def{panic function} (see @Lid{lua_atpanic})
|
|
|
+and then calls @T{abort},
|
|
|
+thus exiting the host application.
|
|
|
+Your panic function can avoid this exit by
|
|
|
+never returning
|
|
|
+(e.g., doing a long jump to your own recovery point outside Lua).
|
|
|
+
|
|
|
+The panic function,
|
|
|
+as its name implies,
|
|
|
+is a mechanism of last resort.
|
|
|
+Programs should avoid it.
|
|
|
+As a general rule,
|
|
|
+when a @N{C function} is called by Lua with a Lua state,
|
|
|
+it can do whatever it wants on that Lua state,
|
|
|
+as it should be already protected.
|
|
|
+However,
|
|
|
+when C code operates on other Lua states
|
|
|
+(e.g., a Lua parameter to the function,
|
|
|
+a Lua state stored in the registry, or
|
|
|
+the result of @Lid{lua_newthread}),
|
|
|
+it should use them only in API calls that cannot raise errors.
|
|
|
+
|
|
|
+The panic function runs as if it were a @x{message handler} @see{error};
|
|
|
+in particular, the error object is at the top of the stack.
|
|
|
+However, there is no guarantee about stack space.
|
|
|
+To push anything on the stack,
|
|
|
+the panic function must first check the available space @see{stacksize}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{continuations|@title{Handling Yields in C}
|
|
|
+
|
|
|
+Internally, Lua uses the C @id{longjmp} facility to yield a coroutine.
|
|
|
+Therefore, if a @N{C function} @id{foo} calls an API function
|
|
|
+and this API function yields
|
|
|
+(directly or indirectly by calling another function that yields),
|
|
|
+Lua cannot return to @id{foo} any more,
|
|
|
+because the @id{longjmp} removes its frame from the C stack.
|
|
|
+
|
|
|
+To avoid this kind of problem,
|
|
|
+Lua raises an error whenever it tries to yield across an API call,
|
|
|
+except for three functions:
|
|
|
+@Lid{lua_yieldk}, @Lid{lua_callk}, and @Lid{lua_pcallk}.
|
|
|
+All those functions receive a @def{continuation function}
|
|
|
+(as a parameter named @id{k}) to continue execution after a yield.
|
|
|
+
|
|
|
+We need to set some terminology to explain continuations.
|
|
|
+We have a @N{C function} called from Lua which we will call
|
|
|
+the @emph{original function}.
|
|
|
+This original function then calls one of those three functions in the C API,
|
|
|
+which we will call the @emph{callee function},
|
|
|
+that then yields the current thread.
|
|
|
+(This can happen when the callee function is @Lid{lua_yieldk},
|
|
|
+or when the callee function is either @Lid{lua_callk} or @Lid{lua_pcallk}
|
|
|
+and the function called by them yields.)
|
|
|
+
|
|
|
+Suppose the running thread yields while executing the callee function.
|
|
|
+After the thread resumes,
|
|
|
+it eventually will finish running the callee function.
|
|
|
+However,
|
|
|
+the callee function cannot return to the original function,
|
|
|
+because its frame in the C stack was destroyed by the yield.
|
|
|
+Instead, Lua calls a @def{continuation function},
|
|
|
+which was given as an argument to the callee function.
|
|
|
+As the name implies,
|
|
|
+the continuation function should continue the task
|
|
|
+of the original function.
|
|
|
+
|
|
|
+As an illustration, consider the following function:
|
|
|
+@verbatim{
|
|
|
+int original_function (lua_State *L) {
|
|
|
+ ... /* code 1 */
|
|
|
+ status = lua_pcall(L, n, m, h); /* calls Lua */
|
|
|
+ ... /* code 2 */
|
|
|
+}
|
|
|
+}
|
|
|
+Now we want to allow
|
|
|
+the Lua code being run by @Lid{lua_pcall} to yield.
|
|
|
+First, we can rewrite our function like here:
|
|
|
+@verbatim{
|
|
|
+int k (lua_State *L, int status, lua_KContext ctx) {
|
|
|
+ ... /* code 2 */
|
|
|
+}
|
|
|
+
|
|
|
+int original_function (lua_State *L) {
|
|
|
+ ... /* code 1 */
|
|
|
+ return k(L, lua_pcall(L, n, m, h), ctx);
|
|
|
+}
|
|
|
+}
|
|
|
+In the above code,
|
|
|
+the new function @id{k} is a
|
|
|
+@emph{continuation function} (with type @Lid{lua_KFunction}),
|
|
|
+which should do all the work that the original function
|
|
|
+was doing after calling @Lid{lua_pcall}.
|
|
|
+Now, we must inform Lua that it must call @id{k} if the Lua code
|
|
|
+being executed by @Lid{lua_pcall} gets interrupted in some way
|
|
|
+(errors or yielding),
|
|
|
+so we rewrite the code as here,
|
|
|
+replacing @Lid{lua_pcall} by @Lid{lua_pcallk}:
|
|
|
+@verbatim{
|
|
|
+int original_function (lua_State *L) {
|
|
|
+ ... /* code 1 */
|
|
|
+ return k(L, lua_pcallk(L, n, m, h, ctx2, k), ctx1);
|
|
|
+}
|
|
|
+}
|
|
|
+Note the external, explicit call to the continuation:
|
|
|
+Lua will call the continuation only if needed, that is,
|
|
|
+in case of errors or resuming after a yield.
|
|
|
+If the called function returns normally without ever yielding,
|
|
|
+@Lid{lua_pcallk} (and @Lid{lua_callk}) will also return normally.
|
|
|
+(Of course, instead of calling the continuation in that case,
|
|
|
+you can do the equivalent work directly inside the original function.)
|
|
|
+
|
|
|
+Besides the Lua state,
|
|
|
+the continuation function has two other parameters:
|
|
|
+the final status of the call plus the context value (@id{ctx}) that
|
|
|
+was passed originally to @Lid{lua_pcallk}.
|
|
|
+(Lua does not use this context value;
|
|
|
+it only passes this value from the original function to the
|
|
|
+continuation function.)
|
|
|
+For @Lid{lua_pcallk},
|
|
|
+the status is the same value that would be returned by @Lid{lua_pcallk},
|
|
|
+except that it is @Lid{LUA_YIELD} when being executed after a yield
|
|
|
+(instead of @Lid{LUA_OK}).
|
|
|
+For @Lid{lua_yieldk} and @Lid{lua_callk},
|
|
|
+the status is always @Lid{LUA_YIELD} when Lua calls the continuation.
|
|
|
+(For these two functions,
|
|
|
+Lua will not call the continuation in case of errors,
|
|
|
+because they do not handle errors.)
|
|
|
+Similarly, when using @Lid{lua_callk},
|
|
|
+you should call the continuation function
|
|
|
+with @Lid{LUA_OK} as the status.
|
|
|
+(For @Lid{lua_yieldk}, there is not much point in calling
|
|
|
+directly the continuation function,
|
|
|
+because @Lid{lua_yieldk} usually does not return.)
|
|
|
+
|
|
|
+Lua treats the continuation function as if it were the original function.
|
|
|
+The continuation function receives the same Lua stack
|
|
|
+from the original function,
|
|
|
+in the same state it would be if the callee function had returned.
|
|
|
+(For instance,
|
|
|
+after a @Lid{lua_callk} the function and its arguments are
|
|
|
+removed from the stack and replaced by the results from the call.)
|
|
|
+It also has the same upvalues.
|
|
|
+Whatever it returns is handled by Lua as if it were the return
|
|
|
+of the original function.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{@title{Functions and Types}
|
|
|
+
|
|
|
+Here we list all functions and types from the @N{C API} in
|
|
|
+alphabetical order.
|
|
|
+Each function has an indicator like this:
|
|
|
+@apii{o,p,x}
|
|
|
+
|
|
|
+The first field, @T{o},
|
|
|
+is how many elements the function pops from the stack.
|
|
|
+The second field, @T{p},
|
|
|
+is how many elements the function pushes onto the stack.
|
|
|
+(Any function always pushes its results after popping its arguments.)
|
|
|
+A field in the form @T{x|y} means the function can push (or pop)
|
|
|
+@T{x} or @T{y} elements,
|
|
|
+depending on the situation;
|
|
|
+an interrogation mark @Char{?} means that
|
|
|
+we cannot know how many elements the function pops/pushes
|
|
|
+by looking only at its arguments
|
|
|
+(e.g., they may depend on what is on the stack).
|
|
|
+The third field, @T{x},
|
|
|
+tells whether the function may raise errors:
|
|
|
+@Char{-} means the function never raises any error;
|
|
|
+@Char{m} means the function may raise out-of-memory errors
|
|
|
+and errors running a finalizer;
|
|
|
+@Char{v} means the function may raise the errors explained in the text;
|
|
|
+@Char{e} means the function may raise any errors
|
|
|
+(because it can run arbitrary Lua code,
|
|
|
+either directly or through metamethods).
|
|
|
+
|
|
|
+
|
|
|
+@APIEntry{int lua_absindex (lua_State *L, int idx);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Converts the @x{acceptable index} @id{idx}
|
|
|
+into an equivalent @x{absolute index}
|
|
|
+(that is, one that does not depend on the stack top).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+typedef void * (*lua_Alloc) (void *ud,
|
|
|
+ void *ptr,
|
|
|
+ size_t osize,
|
|
|
+ size_t nsize);|
|
|
|
+
|
|
|
+The type of the @x{memory-allocation function} used by Lua states.
|
|
|
+The allocator function must provide a
|
|
|
+functionality similar to @id{realloc},
|
|
|
+but not exactly the same.
|
|
|
+Its arguments are
|
|
|
+@id{ud}, an opaque pointer passed to @Lid{lua_newstate};
|
|
|
+@id{ptr}, a pointer to the block being allocated/reallocated/freed;
|
|
|
+@id{osize}, the original size of the block or some code about what
|
|
|
+is being allocated;
|
|
|
+and @id{nsize}, the new size of the block.
|
|
|
+
|
|
|
+When @id{ptr} is not @id{NULL},
|
|
|
+@id{osize} is the size of the block pointed by @id{ptr},
|
|
|
+that is, the size given when it was allocated or reallocated.
|
|
|
+
|
|
|
+When @id{ptr} is @id{NULL},
|
|
|
+@id{osize} encodes the kind of object that Lua is allocating.
|
|
|
+@id{osize} is any of
|
|
|
+@Lid{LUA_TSTRING}, @Lid{LUA_TTABLE}, @Lid{LUA_TFUNCTION},
|
|
|
+@Lid{LUA_TUSERDATA}, or @Lid{LUA_TTHREAD} when (and only when)
|
|
|
+Lua is creating a new object of that type.
|
|
|
+When @id{osize} is some other value,
|
|
|
+Lua is allocating memory for something else.
|
|
|
+
|
|
|
+Lua assumes the following behavior from the allocator function:
|
|
|
+
|
|
|
+When @id{nsize} is zero,
|
|
|
+the allocator must behave like @id{free}
|
|
|
+and return @id{NULL}.
|
|
|
+
|
|
|
+When @id{nsize} is not zero,
|
|
|
+the allocator must behave like @id{realloc}.
|
|
|
+The allocator returns @id{NULL}
|
|
|
+if and only if it cannot fulfill the request.
|
|
|
+
|
|
|
+Here is a simple implementation for the @x{allocator function}.
|
|
|
+It is used in the auxiliary library by @Lid{luaL_newstate}.
|
|
|
+@verbatim{
|
|
|
+static void *l_alloc (void *ud, void *ptr, size_t osize,
|
|
|
+ size_t nsize) {
|
|
|
+ (void)ud; (void)osize; /* not used */
|
|
|
+ if (nsize == 0) {
|
|
|
+ free(ptr);
|
|
|
+ return NULL;
|
|
|
+ }
|
|
|
+ else
|
|
|
+ return realloc(ptr, nsize);
|
|
|
+}
|
|
|
+}
|
|
|
+Note that @N{Standard C} ensures
|
|
|
+that @T{free(NULL)} has no effect and that
|
|
|
+@T{realloc(NULL,size)} is equivalent to @T{malloc(size)}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_arith (lua_State *L, int op);|
|
|
|
+@apii{2|1,1,e}
|
|
|
+
|
|
|
+Performs an arithmetic or bitwise operation over the two values
|
|
|
+(or one, in the case of negations)
|
|
|
+at the top of the stack,
|
|
|
+with the value at the top being the second operand,
|
|
|
+pops these values, and pushes the result of the operation.
|
|
|
+The function follows the semantics of the corresponding Lua operator
|
|
|
+(that is, it may call metamethods).
|
|
|
+
|
|
|
+The value of @id{op} must be one of the following constants:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@defid{LUA_OPADD}| performs addition (@T{+})}
|
|
|
+@item{@defid{LUA_OPSUB}| performs subtraction (@T{-})}
|
|
|
+@item{@defid{LUA_OPMUL}| performs multiplication (@T{*})}
|
|
|
+@item{@defid{LUA_OPDIV}| performs float division (@T{/})}
|
|
|
+@item{@defid{LUA_OPIDIV}| performs floor division (@T{//})}
|
|
|
+@item{@defid{LUA_OPMOD}| performs modulo (@T{%})}
|
|
|
+@item{@defid{LUA_OPPOW}| performs exponentiation (@T{^})}
|
|
|
+@item{@defid{LUA_OPUNM}| performs mathematical negation (unary @T{-})}
|
|
|
+@item{@defid{LUA_OPBNOT}| performs bitwise NOT (@T{~})}
|
|
|
+@item{@defid{LUA_OPBAND}| performs bitwise AND (@T{&})}
|
|
|
+@item{@defid{LUA_OPBOR}| performs bitwise OR (@T{|})}
|
|
|
+@item{@defid{LUA_OPBXOR}| performs bitwise exclusive OR (@T{~})}
|
|
|
+@item{@defid{LUA_OPSHL}| performs left shift (@T{<<})}
|
|
|
+@item{@defid{LUA_OPSHR}| performs right shift (@T{>>})}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Sets a new panic function and returns the old one @see{C-error}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_call (lua_State *L, int nargs, int nresults);|
|
|
|
+@apii{nargs+1,nresults,e}
|
|
|
+
|
|
|
+Calls a function.
|
|
|
+
|
|
|
+To do a call you must use the following protocol:
|
|
|
+first, the value to be called is pushed onto the stack;
|
|
|
+then, the arguments to the call are pushed
|
|
|
+in direct order;
|
|
|
+that is, the first argument is pushed first.
|
|
|
+Finally you call @Lid{lua_call};
|
|
|
+@id{nargs} is the number of arguments that you pushed onto the stack.
|
|
|
+All arguments and the function value are popped from the stack
|
|
|
+when the function is called.
|
|
|
+The function results are pushed onto the stack when the function returns.
|
|
|
+The number of results is adjusted to @id{nresults},
|
|
|
+unless @id{nresults} is @defid{LUA_MULTRET}.
|
|
|
+In this case, all results from the function are pushed;
|
|
|
+Lua takes care that the returned values fit into the stack space,
|
|
|
+but it does not ensure any extra space in the stack.
|
|
|
+The function results are pushed onto the stack in direct order
|
|
|
+(the first result is pushed first),
|
|
|
+so that after the call the last result is on the top of the stack.
|
|
|
+
|
|
|
+Any error while calling and running the function is propagated upwards
|
|
|
+(with a @id{longjmp}).
|
|
|
+Like regular Lua calls,
|
|
|
+this function respects the @idx{__call} metamethod.
|
|
|
+
|
|
|
+The following example shows how the host program can do the
|
|
|
+equivalent to this Lua code:
|
|
|
+@verbatim{
|
|
|
+a = f("how", t.x, 14)
|
|
|
+}
|
|
|
+Here it is @N{in C}:
|
|
|
+@verbatim{
|
|
|
+lua_getglobal(L, "f"); /* function to be called */
|
|
|
+lua_pushliteral(L, "how"); /* 1st argument */
|
|
|
+lua_getglobal(L, "t"); /* table to be indexed */
|
|
|
+lua_getfield(L, -1, "x"); /* push result of t.x (2nd arg) */
|
|
|
+lua_remove(L, -2); /* remove 't' from the stack */
|
|
|
+lua_pushinteger(L, 14); /* 3rd argument */
|
|
|
+lua_call(L, 3, 1); /* call 'f' with 3 arguments and 1 result */
|
|
|
+lua_setglobal(L, "a"); /* set global 'a' */
|
|
|
+}
|
|
|
+Note that the code above is @emph{balanced}:
|
|
|
+at its end, the stack is back to its original configuration.
|
|
|
+This is considered good programming practice.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+void lua_callk (lua_State *L,
|
|
|
+ int nargs,
|
|
|
+ int nresults,
|
|
|
+ lua_KContext ctx,
|
|
|
+ lua_KFunction k);|
|
|
|
+@apii{nargs + 1,nresults,e}
|
|
|
+
|
|
|
+This function behaves exactly like @Lid{lua_call},
|
|
|
+but allows the called function to yield @see{continuations}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{typedef int (*lua_CFunction) (lua_State *L);|
|
|
|
+
|
|
|
+Type for @N{C functions}.
|
|
|
+
|
|
|
+In order to communicate properly with Lua,
|
|
|
+a @N{C function} must use the following protocol,
|
|
|
+which defines the way parameters and results are passed:
|
|
|
+a @N{C function} receives its arguments from Lua in its stack
|
|
|
+in direct order (the first argument is pushed first).
|
|
|
+So, when the function starts,
|
|
|
+@T{lua_gettop(L)} returns the number of arguments received by the function.
|
|
|
+The first argument (if any) is at index 1
|
|
|
+and its last argument is at index @T{lua_gettop(L)}.
|
|
|
+To return values to Lua, a @N{C function} just pushes them onto the stack,
|
|
|
+in direct order (the first result is pushed first),
|
|
|
+and returns the number of results.
|
|
|
+Any other value in the stack below the results will be properly
|
|
|
+discarded by Lua.
|
|
|
+Like a Lua function, a @N{C function} called by Lua can also return
|
|
|
+many results.
|
|
|
+
|
|
|
+As an example, the following function receives a variable number
|
|
|
+of numeric arguments and returns their average and their sum:
|
|
|
+@verbatim{
|
|
|
+static int foo (lua_State *L) {
|
|
|
+ int n = lua_gettop(L); /* number of arguments */
|
|
|
+ lua_Number sum = 0.0;
|
|
|
+ int i;
|
|
|
+ for (i = 1; i <= n; i++) {
|
|
|
+ if (!lua_isnumber(L, i)) {
|
|
|
+ lua_pushliteral(L, "incorrect argument");
|
|
|
+ lua_error(L);
|
|
|
+ }
|
|
|
+ sum += lua_tonumber(L, i);
|
|
|
+ }
|
|
|
+ lua_pushnumber(L, sum/n); /* first result */
|
|
|
+ lua_pushnumber(L, sum); /* second result */
|
|
|
+ return 2; /* number of results */
|
|
|
+}
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@APIEntry{int lua_checkstack (lua_State *L, int n);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Ensures that the stack has space for at least @id{n} extra slots
|
|
|
+(that is, that you can safely push up to @id{n} values into it).
|
|
|
+It returns false if it cannot fulfill the request,
|
|
|
+either because it would cause the stack
|
|
|
+to be larger than a fixed maximum size
|
|
|
+(typically at least several thousand elements) or
|
|
|
+because it cannot allocate memory for the extra space.
|
|
|
+This function never shrinks the stack;
|
|
|
+if the stack already has space for the extra slots,
|
|
|
+it is left unchanged.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_close (lua_State *L);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Destroys all objects in the given Lua state
|
|
|
+(calling the corresponding garbage-collection metamethods, if any)
|
|
|
+and frees all dynamic memory used by this state.
|
|
|
+On several platforms, you may not need to call this function,
|
|
|
+because all resources are naturally released when the host program ends.
|
|
|
+On the other hand, long-running programs that create multiple states,
|
|
|
+such as daemons or web servers,
|
|
|
+will probably need to close states as soon as they are not needed.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_compare (lua_State *L, int index1, int index2, int op);|
|
|
|
+@apii{0,0,e}
|
|
|
+
|
|
|
+Compares two Lua values.
|
|
|
+Returns 1 if the value at index @id{index1} satisfies @id{op}
|
|
|
+when compared with the value at index @id{index2},
|
|
|
+following the semantics of the corresponding Lua operator
|
|
|
+(that is, it may call metamethods).
|
|
|
+Otherwise @N{returns 0}.
|
|
|
+Also @N{returns 0} if any of the indices is not valid.
|
|
|
+
|
|
|
+The value of @id{op} must be one of the following constants:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@defid{LUA_OPEQ}| compares for equality (@T{==})}
|
|
|
+@item{@defid{LUA_OPLT}| compares for less than (@T{<})}
|
|
|
+@item{@defid{LUA_OPLE}| compares for less or equal (@T{<=})}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_concat (lua_State *L, int n);|
|
|
|
+@apii{n,1,e}
|
|
|
+
|
|
|
+Concatenates the @id{n} values at the top of the stack,
|
|
|
+pops them, and leaves the result at the top.
|
|
|
+If @N{@T{n} is 1}, the result is the single value on the stack
|
|
|
+(that is, the function does nothing);
|
|
|
+if @id{n} is 0, the result is the empty string.
|
|
|
+Concatenation is performed following the usual semantics of Lua
|
|
|
+@see{concat}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_copy (lua_State *L, int fromidx, int toidx);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Copies the element at index @id{fromidx}
|
|
|
+into the valid index @id{toidx},
|
|
|
+replacing the value at that position.
|
|
|
+Values at other positions are not affected.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_createtable (lua_State *L, int narr, int nrec);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Creates a new empty table and pushes it onto the stack.
|
|
|
+Parameter @id{narr} is a hint for how many elements the table
|
|
|
+will have as a sequence;
|
|
|
+parameter @id{nrec} is a hint for how many other elements
|
|
|
+the table will have.
|
|
|
+Lua may use these hints to preallocate memory for the new table.
|
|
|
+This preallocation is useful for performance when you know in advance
|
|
|
+how many elements the table will have.
|
|
|
+Otherwise you can use the function @Lid{lua_newtable}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_dump (lua_State *L,
|
|
|
+ lua_Writer writer,
|
|
|
+ void *data,
|
|
|
+ int strip);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Dumps a function as a binary chunk.
|
|
|
+Receives a Lua function on the top of the stack
|
|
|
+and produces a binary chunk that,
|
|
|
+if loaded again,
|
|
|
+results in a function equivalent to the one dumped.
|
|
|
+As it produces parts of the chunk,
|
|
|
+@Lid{lua_dump} calls function @id{writer} @seeC{lua_Writer}
|
|
|
+with the given @id{data}
|
|
|
+to write them.
|
|
|
+
|
|
|
+If @id{strip} is true,
|
|
|
+the binary representation may not include all debug information
|
|
|
+about the function,
|
|
|
+to save space.
|
|
|
+
|
|
|
+The value returned is the error code returned by the last
|
|
|
+call to the writer;
|
|
|
+@N{0 means} no errors.
|
|
|
+
|
|
|
+This function does not pop the Lua function from the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_error (lua_State *L);|
|
|
|
+@apii{1,0,v}
|
|
|
+
|
|
|
+Generates a Lua error,
|
|
|
+using the value at the top of the stack as the error object.
|
|
|
+This function does a long jump,
|
|
|
+and therefore never returns
|
|
|
+@seeC{luaL_error}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_gc (lua_State *L, int what, int data);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Controls the garbage collector.
|
|
|
+
|
|
|
+This function performs several tasks,
|
|
|
+according to the value of the parameter @id{what}:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@id{LUA_GCSTOP}|
|
|
|
+stops the garbage collector.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{LUA_GCRESTART}|
|
|
|
+restarts the garbage collector.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{LUA_GCCOLLECT}|
|
|
|
+performs a full garbage-collection cycle.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{LUA_GCCOUNT}|
|
|
|
+returns the current amount of memory (in Kbytes) in use by Lua.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{LUA_GCCOUNTB}|
|
|
|
+returns the remainder of dividing the current amount of bytes of
|
|
|
+memory in use by Lua by 1024.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{LUA_GCSTEP}|
|
|
|
+performs an incremental step of garbage collection.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{LUA_GCSETPAUSE}|
|
|
|
+sets @id{data} as the new value
|
|
|
+for the @emph{pause} of the collector @see{GC}
|
|
|
+and returns the previous value of the pause.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{LUA_GCSETSTEPMUL}|
|
|
|
+sets @id{data} as the new value for the @emph{step multiplier} of
|
|
|
+the collector @see{GC}
|
|
|
+and returns the previous value of the step multiplier.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{LUA_GCISRUNNING}|
|
|
|
+returns a boolean that tells whether the collector is running
|
|
|
+(i.e., not stopped).
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+For more details about these options,
|
|
|
+see @Lid{collectgarbage}.
|
|
|
+
|
|
|
+This function may raise errors when calling finalizers.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Alloc lua_getallocf (lua_State *L, void **ud);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the @x{memory-allocation function} of a given state.
|
|
|
+If @id{ud} is not @id{NULL}, Lua stores in @T{*ud} the
|
|
|
+opaque pointer given when the memory-allocator function was set.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_getfield (lua_State *L, int index, const char *k);|
|
|
|
+@apii{0,1,e}
|
|
|
+
|
|
|
+Pushes onto the stack the value @T{t[k]},
|
|
|
+where @id{t} is the value at the given index.
|
|
|
+As in Lua, this function may trigger a metamethod
|
|
|
+for the @Q{index} event @see{metatable}.
|
|
|
+
|
|
|
+Returns the type of the pushed value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void *lua_getextraspace (lua_State *L);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns a pointer to a raw memory area associated with the
|
|
|
+given Lua state.
|
|
|
+The application can use this area for any purpose;
|
|
|
+Lua does not use it for anything.
|
|
|
+
|
|
|
+Each new thread has this area initialized with a copy
|
|
|
+of the area of the @x{main thread}.
|
|
|
+
|
|
|
+By default, this area has the size of a pointer to void,
|
|
|
+but you can recompile Lua with a different size for this area.
|
|
|
+(See @id{LUA_EXTRASPACE} in @id{luaconf.h}.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_getglobal (lua_State *L, const char *name);|
|
|
|
+@apii{0,1,e}
|
|
|
+
|
|
|
+Pushes onto the stack the value of the global @id{name}.
|
|
|
+Returns the type of that value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_geti (lua_State *L, int index, lua_Integer i);|
|
|
|
+@apii{0,1,e}
|
|
|
+
|
|
|
+Pushes onto the stack the value @T{t[i]},
|
|
|
+where @id{t} is the value at the given index.
|
|
|
+As in Lua, this function may trigger a metamethod
|
|
|
+for the @Q{index} event @see{metatable}.
|
|
|
+
|
|
|
+Returns the type of the pushed value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_getmetatable (lua_State *L, int index);|
|
|
|
+@apii{0,0|1,-}
|
|
|
+
|
|
|
+If the value at the given index has a metatable,
|
|
|
+the function pushes that metatable onto the stack and @N{returns 1}.
|
|
|
+Otherwise,
|
|
|
+the function @N{returns 0} and pushes nothing on the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_gettable (lua_State *L, int index);|
|
|
|
+@apii{1,1,e}
|
|
|
+
|
|
|
+Pushes onto the stack the value @T{t[k]},
|
|
|
+where @id{t} is the value at the given index
|
|
|
+and @id{k} is the value at the top of the stack.
|
|
|
+
|
|
|
+This function pops the key from the stack,
|
|
|
+pushing the resulting value in its place.
|
|
|
+As in Lua, this function may trigger a metamethod
|
|
|
+for the @Q{index} event @see{metatable}.
|
|
|
+
|
|
|
+Returns the type of the pushed value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_gettop (lua_State *L);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the index of the top element in the stack.
|
|
|
+Because indices start @N{at 1},
|
|
|
+this result is equal to the number of elements in the stack;
|
|
|
+in particular, @N{0 means} an empty stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_getiuservalue (lua_State *L, int index, int n);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes onto the stack the @id{n}-th user value associated with the
|
|
|
+full userdata at the given index and
|
|
|
+returns the type of the pushed value.
|
|
|
+
|
|
|
+If the userdata does not have that value,
|
|
|
+pushes @nil and returns @Lid{LUA_TNONE}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_insert (lua_State *L, int index);|
|
|
|
+@apii{1,1,-}
|
|
|
+
|
|
|
+Moves the top element into the given valid index,
|
|
|
+shifting up the elements above this index to open space.
|
|
|
+This function cannot be called with a pseudo-index,
|
|
|
+because a pseudo-index is not an actual stack position.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{typedef @ldots lua_Integer;|
|
|
|
+
|
|
|
+The type of integers in Lua.
|
|
|
+
|
|
|
+By default this type is @id{long long},
|
|
|
+(usually a 64-bit two-complement integer),
|
|
|
+but that can be changed to @id{long} or @id{int}
|
|
|
+(usually a 32-bit two-complement integer).
|
|
|
+(See @id{LUA_INT_TYPE} in @id{luaconf.h}.)
|
|
|
+
|
|
|
+Lua also defines the constants
|
|
|
+@defid{LUA_MININTEGER} and @defid{LUA_MAXINTEGER},
|
|
|
+with the minimum and the maximum values that fit in this type.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isboolean (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is a boolean,
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_iscfunction (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is a @N{C function},
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isfunction (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is a function
|
|
|
+(either C or Lua), and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isinteger (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is an integer
|
|
|
+(that is, the value is a number and is represented as an integer),
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_islightuserdata (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is a light userdata,
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isnil (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is @nil,
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isnone (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the given index is not valid,
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isnoneornil (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the given index is not valid
|
|
|
+or if the value at this index is @nil,
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isnumber (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is a number
|
|
|
+or a string convertible to a number,
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isstring (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is a string
|
|
|
+or a number (which is always convertible to a string),
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_istable (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is a table,
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isthread (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is a thread,
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isuserdata (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the value at the given index is a userdata
|
|
|
+(either full or light), and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_isyieldable (lua_State *L);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the given coroutine can yield,
|
|
|
+and @N{0 otherwise}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{typedef @ldots lua_KContext;|
|
|
|
+
|
|
|
+The type for continuation-function contexts.
|
|
|
+It must be a numeric type.
|
|
|
+This type is defined as @id{intptr_t}
|
|
|
+when @id{intptr_t} is available,
|
|
|
+so that it can store pointers too.
|
|
|
+Otherwise, it is defined as @id{ptrdiff_t}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+typedef int (*lua_KFunction) (lua_State *L, int status, lua_KContext ctx);|
|
|
|
+
|
|
|
+Type for continuation functions @see{continuations}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_len (lua_State *L, int index);|
|
|
|
+@apii{0,1,e}
|
|
|
+
|
|
|
+Returns the length of the value at the given index.
|
|
|
+It is equivalent to the @Char{#} operator in Lua @see{len-op} and
|
|
|
+may trigger a metamethod for the @Q{length} event @see{metatable}.
|
|
|
+The result is pushed on the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+int lua_load (lua_State *L,
|
|
|
+ lua_Reader reader,
|
|
|
+ void *data,
|
|
|
+ const char *chunkname,
|
|
|
+ const char *mode);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Loads a Lua chunk without running it.
|
|
|
+If there are no errors,
|
|
|
+@id{lua_load} pushes the compiled chunk as a Lua
|
|
|
+function on top of the stack.
|
|
|
+Otherwise, it pushes an error message.
|
|
|
+
|
|
|
+The return values of @id{lua_load} are:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@Lid{LUA_OK}| no errors;}
|
|
|
+
|
|
|
+@item{@defid{LUA_ERRSYNTAX}|
|
|
|
+syntax error during precompilation;}
|
|
|
+
|
|
|
+@item{@Lid{LUA_ERRMEM}|
|
|
|
+@x{memory allocation (out-of-memory) error};}
|
|
|
+
|
|
|
+@item{@Lid{LUA_ERRGCMM}|
|
|
|
+error while running a @idx{__gc} metamethod.
|
|
|
+(This error has no relation with the chunk being loaded.
|
|
|
+It is generated by the garbage collector.)
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+The @id{lua_load} function uses a user-supplied @id{reader} function
|
|
|
+to read the chunk @seeC{lua_Reader}.
|
|
|
+The @id{data} argument is an opaque value passed to the reader function.
|
|
|
+
|
|
|
+The @id{chunkname} argument gives a name to the chunk,
|
|
|
+which is used for error messages and in debug information @see{debugI}.
|
|
|
+
|
|
|
+@id{lua_load} automatically detects whether the chunk is text or binary
|
|
|
+and loads it accordingly (see program @idx{luac}).
|
|
|
+The string @id{mode} works as in function @Lid{load},
|
|
|
+with the addition that
|
|
|
+a @id{NULL} value is equivalent to the string @St{bt}.
|
|
|
+
|
|
|
+@id{lua_load} uses the stack internally,
|
|
|
+so the reader function must always leave the stack
|
|
|
+unmodified when returning.
|
|
|
+
|
|
|
+If the resulting function has upvalues,
|
|
|
+its first upvalue is set to the value of the @x{global environment}
|
|
|
+stored at index @id{LUA_RIDX_GLOBALS} in the registry @see{registry}.
|
|
|
+When loading main chunks,
|
|
|
+this upvalue will be the @id{_ENV} variable @see{globalenv}.
|
|
|
+Other upvalues are initialized with @nil.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_State *lua_newstate (lua_Alloc f, void *ud);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Creates a new thread running in a new, independent state.
|
|
|
+Returns @id{NULL} if it cannot create the thread or the state
|
|
|
+(due to lack of memory).
|
|
|
+The argument @id{f} is the @x{allocator function};
|
|
|
+Lua does all memory allocation for this state
|
|
|
+through this function @seeF{lua_Alloc}.
|
|
|
+The second argument, @id{ud}, is an opaque pointer that Lua
|
|
|
+passes to the allocator in every call.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_newtable (lua_State *L);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Creates a new empty table and pushes it onto the stack.
|
|
|
+It is equivalent to @T{lua_createtable(L, 0, 0)}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_State *lua_newthread (lua_State *L);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Creates a new thread, pushes it on the stack,
|
|
|
+and returns a pointer to a @Lid{lua_State} that represents this new thread.
|
|
|
+The new thread returned by this function shares with the original thread
|
|
|
+its global environment,
|
|
|
+but has an independent execution stack.
|
|
|
+
|
|
|
+There is no explicit function to close or to destroy a thread.
|
|
|
+Threads are subject to garbage collection,
|
|
|
+like any Lua object.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void *lua_newuserdatauv (lua_State *L, size_t size, int nuvalue);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+This function creates and pushes on the stack a new full userdata,
|
|
|
+with @id{nuvalue} associated Lua values (called @id{user values})
|
|
|
+plus an associated block of raw memory with @id{size} bytes.
|
|
|
+(The user values can be set and read with the functions
|
|
|
+@Lid{lua_setiuservalue} and @Lid{lua_getiuservalue}.)
|
|
|
+
|
|
|
+The function returns the address of the block of memory.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_next (lua_State *L, int index);|
|
|
|
+@apii{1,2|0,v}
|
|
|
+
|
|
|
+Pops a key from the stack,
|
|
|
+and pushes a key@En{}value pair from the table at the given index
|
|
|
+(the @Q{next} pair after the given key).
|
|
|
+If there are no more elements in the table,
|
|
|
+then @Lid{lua_next} returns 0 (and pushes nothing).
|
|
|
+
|
|
|
+A typical traversal looks like this:
|
|
|
+@verbatim{
|
|
|
+/* table is in the stack at index 't' */
|
|
|
+lua_pushnil(L); /* first key */
|
|
|
+while (lua_next(L, t) != 0) {
|
|
|
+ /* uses 'key' (at index -2) and 'value' (at index -1) */
|
|
|
+ printf("%s - %s\n",
|
|
|
+ lua_typename(L, lua_type(L, -2)),
|
|
|
+ lua_typename(L, lua_type(L, -1)));
|
|
|
+ /* removes 'value'; keeps 'key' for next iteration */
|
|
|
+ lua_pop(L, 1);
|
|
|
+}
|
|
|
+}
|
|
|
+
|
|
|
+While traversing a table,
|
|
|
+do not call @Lid{lua_tolstring} directly on a key,
|
|
|
+unless you know that the key is actually a string.
|
|
|
+Recall that @Lid{lua_tolstring} may change
|
|
|
+the value at the given index;
|
|
|
+this confuses the next call to @Lid{lua_next}.
|
|
|
+
|
|
|
+This function may raise an error if the given key
|
|
|
+is neither @nil nor present in the table.
|
|
|
+See function @Lid{next} for the caveats of modifying
|
|
|
+the table during its traversal.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{typedef @ldots lua_Number;|
|
|
|
+
|
|
|
+The type of floats in Lua.
|
|
|
+
|
|
|
+By default this type is double,
|
|
|
+but that can be changed to a single float or a long double.
|
|
|
+(See @id{LUA_FLOAT_TYPE} in @id{luaconf.h}.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_numbertointeger (lua_Number n, lua_Integer *p);|
|
|
|
+
|
|
|
+Converts a Lua float to a Lua integer.
|
|
|
+This macro assumes that @id{n} has an integral value.
|
|
|
+If that value is within the range of Lua integers,
|
|
|
+it is converted to an integer and assigned to @T{*p}.
|
|
|
+The macro results in a boolean indicating whether the
|
|
|
+conversion was successful.
|
|
|
+(Note that this range test can be tricky to do
|
|
|
+correctly without this macro,
|
|
|
+due to roundings.)
|
|
|
+
|
|
|
+This macro may evaluate its arguments more than once.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_pcall (lua_State *L, int nargs, int nresults, int msgh);|
|
|
|
+@apii{nargs + 1,nresults|1,-}
|
|
|
+
|
|
|
+Calls a function (or a callable object) in protected mode.
|
|
|
+
|
|
|
+Both @id{nargs} and @id{nresults} have the same meaning as
|
|
|
+in @Lid{lua_call}.
|
|
|
+If there are no errors during the call,
|
|
|
+@Lid{lua_pcall} behaves exactly like @Lid{lua_call}.
|
|
|
+However, if there is any error,
|
|
|
+@Lid{lua_pcall} catches it,
|
|
|
+pushes a single value on the stack (the error object),
|
|
|
+and returns an error code.
|
|
|
+Like @Lid{lua_call},
|
|
|
+@Lid{lua_pcall} always removes the function
|
|
|
+and its arguments from the stack.
|
|
|
+
|
|
|
+If @id{msgh} is 0,
|
|
|
+then the error object returned on the stack
|
|
|
+is exactly the original error object.
|
|
|
+Otherwise, @id{msgh} is the stack index of a
|
|
|
+@emph{message handler}.
|
|
|
+(This index cannot be a pseudo-index.)
|
|
|
+In case of runtime errors,
|
|
|
+this function will be called with the error object
|
|
|
+and its return value will be the object
|
|
|
+returned on the stack by @Lid{lua_pcall}.
|
|
|
+
|
|
|
+Typically, the message handler is used to add more debug
|
|
|
+information to the error object, such as a stack traceback.
|
|
|
+Such information cannot be gathered after the return of @Lid{lua_pcall},
|
|
|
+since by then the stack has unwound.
|
|
|
+
|
|
|
+The @Lid{lua_pcall} function returns one of the following constants
|
|
|
+(defined in @id{lua.h}):
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@defid{LUA_OK} (0)|
|
|
|
+success.}
|
|
|
+
|
|
|
+@item{@defid{LUA_ERRRUN}|
|
|
|
+a runtime error.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@defid{LUA_ERRMEM}|
|
|
|
+@x{memory allocation error}.
|
|
|
+For such errors, Lua does not call the @x{message handler}.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@defid{LUA_ERRERR}|
|
|
|
+error while running the @x{message handler}.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@defid{LUA_ERRGCMM}|
|
|
|
+error while running a @idx{__gc} metamethod.
|
|
|
+For such errors, Lua does not call the @x{message handler}
|
|
|
+(as this kind of error typically has no relation
|
|
|
+with the function being called).
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+int lua_pcallk (lua_State *L,
|
|
|
+ int nargs,
|
|
|
+ int nresults,
|
|
|
+ int msgh,
|
|
|
+ lua_KContext ctx,
|
|
|
+ lua_KFunction k);|
|
|
|
+@apii{nargs + 1,nresults|1,-}
|
|
|
+
|
|
|
+This function behaves exactly like @Lid{lua_pcall},
|
|
|
+but allows the called function to yield @see{continuations}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pop (lua_State *L, int n);|
|
|
|
+@apii{n,0,-}
|
|
|
+
|
|
|
+Pops @id{n} elements from the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pushboolean (lua_State *L, int b);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes a boolean value with value @id{b} onto the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);|
|
|
|
+@apii{n,1,m}
|
|
|
+
|
|
|
+Pushes a new @N{C closure} onto the stack.
|
|
|
+This function receives a pointer to a @N{C function}
|
|
|
+and pushes onto the stack a Lua value of type @id{function} that,
|
|
|
+when called, invokes the corresponding @N{C function}.
|
|
|
+The parameter @id{n} tells how many upvalues this function will have
|
|
|
+@see{c-closure}.
|
|
|
+
|
|
|
+Any function to be callable by Lua must
|
|
|
+follow the correct protocol to receive its parameters
|
|
|
+and return its results @seeC{lua_CFunction}.
|
|
|
+
|
|
|
+When a @N{C function} is created,
|
|
|
+it is possible to associate some values with it,
|
|
|
+thus creating a @x{@N{C closure}} @see{c-closure};
|
|
|
+these values are then accessible to the function whenever it is called.
|
|
|
+To associate values with a @N{C function},
|
|
|
+first these values must be pushed onto the stack
|
|
|
+(when there are multiple values, the first value is pushed first).
|
|
|
+Then @Lid{lua_pushcclosure}
|
|
|
+is called to create and push the @N{C function} onto the stack,
|
|
|
+with the argument @id{n} telling how many values will be
|
|
|
+associated with the function.
|
|
|
+@Lid{lua_pushcclosure} also pops these values from the stack.
|
|
|
+
|
|
|
+The maximum value for @id{n} is 255.
|
|
|
+
|
|
|
+When @id{n} is zero,
|
|
|
+this function creates a @def{light @N{C function}},
|
|
|
+which is just a pointer to the @N{C function}.
|
|
|
+In that case, it never raises a memory error.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pushcfunction (lua_State *L, lua_CFunction f);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes a @N{C function} onto the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_pushfstring (lua_State *L, const char *fmt, ...);|
|
|
|
+@apii{0,1,v}
|
|
|
+
|
|
|
+Pushes onto the stack a formatted string
|
|
|
+and returns a pointer to this string.
|
|
|
+It is similar to the @ANSI{sprintf},
|
|
|
+but has two important differences.
|
|
|
+First,
|
|
|
+you do not have to allocate space for the result;
|
|
|
+the result is a Lua string and Lua takes care of memory allocation
|
|
|
+(and deallocation, through garbage collection).
|
|
|
+Second,
|
|
|
+the conversion specifiers are quite restricted.
|
|
|
+There are no flags, widths, or precisions.
|
|
|
+The conversion specifiers can only be
|
|
|
+@Char{%%} (inserts the character @Char{%}),
|
|
|
+@Char{%s} (inserts a zero-terminated string, with no size restrictions),
|
|
|
+@Char{%f} (inserts a @Lid{lua_Number}),
|
|
|
+@Char{%I} (inserts a @Lid{lua_Integer}),
|
|
|
+@Char{%p} (inserts a pointer as a hexadecimal numeral),
|
|
|
+@Char{%d} (inserts an @T{int}),
|
|
|
+@Char{%c} (inserts an @T{int} as a one-byte character), and
|
|
|
+@Char{%U} (inserts a @T{long int} as a @x{UTF-8} byte sequence).
|
|
|
+
|
|
|
+This function may raise errors due to memory overflow
|
|
|
+or an invalid conversion specifier.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pushglobaltable (lua_State *L);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes the @x{global environment} onto the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pushinteger (lua_State *L, lua_Integer n);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes an integer with value @id{n} onto the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pushlightuserdata (lua_State *L, void *p);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes a light userdata onto the stack.
|
|
|
+
|
|
|
+Userdata represent @N{C values} in Lua.
|
|
|
+A @def{light userdata} represents a pointer, a @T{void*}.
|
|
|
+It is a value (like a number):
|
|
|
+you do not create it, it has no individual metatable,
|
|
|
+and it is not collected (as it was never created).
|
|
|
+A light userdata is equal to @Q{any}
|
|
|
+light userdata with the same @N{C address}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_pushliteral (lua_State *L, const char *s);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+This macro is equivalent to @Lid{lua_pushstring},
|
|
|
+but should be used only when @id{s} is a literal string.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_pushlstring (lua_State *L, const char *s, size_t len);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Pushes the string pointed to by @id{s} with size @id{len}
|
|
|
+onto the stack.
|
|
|
+Lua makes (or reuses) an internal copy of the given string,
|
|
|
+so the memory at @id{s} can be freed or reused immediately after
|
|
|
+the function returns.
|
|
|
+The string can contain any binary data,
|
|
|
+including @x{embedded zeros}.
|
|
|
+
|
|
|
+Returns a pointer to the internal copy of the string.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pushnil (lua_State *L);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes a nil value onto the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pushnumber (lua_State *L, lua_Number n);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes a float with value @id{n} onto the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_pushstring (lua_State *L, const char *s);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Pushes the zero-terminated string pointed to by @id{s}
|
|
|
+onto the stack.
|
|
|
+Lua makes (or reuses) an internal copy of the given string,
|
|
|
+so the memory at @id{s} can be freed or reused immediately after
|
|
|
+the function returns.
|
|
|
+
|
|
|
+Returns a pointer to the internal copy of the string.
|
|
|
+
|
|
|
+If @id{s} is @id{NULL}, pushes @nil and returns @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_pushthread (lua_State *L);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes the thread represented by @id{L} onto the stack.
|
|
|
+Returns 1 if this thread is the @x{main thread} of its state.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_pushvalue (lua_State *L, int index);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes a copy of the element at the given index
|
|
|
+onto the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+const char *lua_pushvfstring (lua_State *L,
|
|
|
+ const char *fmt,
|
|
|
+ va_list argp);|
|
|
|
+@apii{0,1,v}
|
|
|
+
|
|
|
+Equivalent to @Lid{lua_pushfstring}, except that it receives a @id{va_list}
|
|
|
+instead of a variable number of arguments.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_rawequal (lua_State *L, int index1, int index2);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns 1 if the two values in indices @id{index1} and
|
|
|
+@id{index2} are primitively equal
|
|
|
+(that is, without calling the @idx{__eq} metamethod).
|
|
|
+Otherwise @N{returns 0}.
|
|
|
+Also @N{returns 0} if any of the indices are not valid.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_rawget (lua_State *L, int index);|
|
|
|
+@apii{1,1,-}
|
|
|
+
|
|
|
+Similar to @Lid{lua_gettable}, but does a raw access
|
|
|
+(i.e., without metamethods).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_rawgeti (lua_State *L, int index, lua_Integer n);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes onto the stack the value @T{t[n]},
|
|
|
+where @id{t} is the table at the given index.
|
|
|
+The access is raw,
|
|
|
+that is, it does not invoke the @idx{__index} metamethod.
|
|
|
+
|
|
|
+Returns the type of the pushed value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_rawgetp (lua_State *L, int index, const void *p);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Pushes onto the stack the value @T{t[k]},
|
|
|
+where @id{t} is the table at the given index and
|
|
|
+@id{k} is the pointer @id{p} represented as a light userdata.
|
|
|
+The access is raw;
|
|
|
+that is, it does not invoke the @idx{__index} metamethod.
|
|
|
+
|
|
|
+Returns the type of the pushed value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Unsigned lua_rawlen (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the raw @Q{length} of the value at the given index:
|
|
|
+for strings, this is the string length;
|
|
|
+for tables, this is the result of the length operator (@Char{#})
|
|
|
+with no metamethods;
|
|
|
+for userdata, this is the size of the block of memory allocated
|
|
|
+for the userdata;
|
|
|
+for other values, it @N{is 0}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_rawset (lua_State *L, int index);|
|
|
|
+@apii{2,0,m}
|
|
|
+
|
|
|
+Similar to @Lid{lua_settable}, but does a raw assignment
|
|
|
+(i.e., without metamethods).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_rawseti (lua_State *L, int index, lua_Integer i);|
|
|
|
+@apii{1,0,m}
|
|
|
+
|
|
|
+Does the equivalent of @T{t[i] = v},
|
|
|
+where @id{t} is the table at the given index
|
|
|
+and @id{v} is the value at the top of the stack.
|
|
|
+
|
|
|
+This function pops the value from the stack.
|
|
|
+The assignment is raw,
|
|
|
+that is, it does not invoke the @idx{__newindex} metamethod.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_rawsetp (lua_State *L, int index, const void *p);|
|
|
|
+@apii{1,0,m}
|
|
|
+
|
|
|
+Does the equivalent of @T{t[p] = v},
|
|
|
+where @id{t} is the table at the given index,
|
|
|
+@id{p} is encoded as a light userdata,
|
|
|
+and @id{v} is the value at the top of the stack.
|
|
|
+
|
|
|
+This function pops the value from the stack.
|
|
|
+The assignment is raw,
|
|
|
+that is, it does not invoke @idx{__newindex} metamethod.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+typedef const char * (*lua_Reader) (lua_State *L,
|
|
|
+ void *data,
|
|
|
+ size_t *size);|
|
|
|
+
|
|
|
+The reader function used by @Lid{lua_load}.
|
|
|
+Every time it needs another piece of the chunk,
|
|
|
+@Lid{lua_load} calls the reader,
|
|
|
+passing along its @id{data} parameter.
|
|
|
+The reader must return a pointer to a block of memory
|
|
|
+with a new piece of the chunk
|
|
|
+and set @id{size} to the block size.
|
|
|
+The block must exist until the reader function is called again.
|
|
|
+To signal the end of the chunk,
|
|
|
+the reader must return @id{NULL} or set @id{size} to zero.
|
|
|
+The reader function may return pieces of any size greater than zero.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_register (lua_State *L, const char *name, lua_CFunction f);|
|
|
|
+@apii{0,0,e}
|
|
|
+
|
|
|
+Sets the @N{C function} @id{f} as the new value of global @id{name}.
|
|
|
+It is defined as a macro:
|
|
|
+@verbatim{
|
|
|
+#define lua_register(L,n,f) \
|
|
|
+ (lua_pushcfunction(L, f), lua_setglobal(L, n))
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_remove (lua_State *L, int index);|
|
|
|
+@apii{1,0,-}
|
|
|
+
|
|
|
+Removes the element at the given valid index,
|
|
|
+shifting down the elements above this index to fill the gap.
|
|
|
+This function cannot be called with a pseudo-index,
|
|
|
+because a pseudo-index is not an actual stack position.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_replace (lua_State *L, int index);|
|
|
|
+@apii{1,0,-}
|
|
|
+
|
|
|
+Moves the top element into the given valid index
|
|
|
+without shifting any element
|
|
|
+(therefore replacing the value at that given index),
|
|
|
+and then pops the top element.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_resume (lua_State *L, lua_State *from, int nargs,
|
|
|
+ int *nresults);|
|
|
|
+@apii{?,?,-}
|
|
|
+
|
|
|
+Starts and resumes a coroutine in the given thread @id{L}.
|
|
|
+
|
|
|
+To start a coroutine,
|
|
|
+you push onto the thread stack the main function plus any arguments;
|
|
|
+then you call @Lid{lua_resume},
|
|
|
+with @id{nargs} being the number of arguments.
|
|
|
+This call returns when the coroutine suspends or finishes its execution.
|
|
|
+When it returns,
|
|
|
+@id{nresults} is updated and
|
|
|
+the top of the stack contains
|
|
|
+the @id{nresults} values passed to @Lid{lua_yield}
|
|
|
+or returned by the body function.
|
|
|
+@Lid{lua_resume} returns
|
|
|
+@Lid{LUA_YIELD} if the coroutine yields,
|
|
|
+@Lid{LUA_OK} if the coroutine finishes its execution
|
|
|
+without errors,
|
|
|
+or an error code in case of errors @seeC{lua_pcall}.
|
|
|
+
|
|
|
+In case of errors,
|
|
|
+the stack is not unwound,
|
|
|
+so you can use the debug API over it.
|
|
|
+The error object is on the top of the stack.
|
|
|
+
|
|
|
+To resume a coroutine,
|
|
|
+you remove all results from the last @Lid{lua_yield},
|
|
|
+put on its stack only the values to
|
|
|
+be passed as results from @id{yield},
|
|
|
+and then call @Lid{lua_resume}.
|
|
|
+
|
|
|
+The parameter @id{from} represents the coroutine that is resuming @id{L}.
|
|
|
+If there is no such coroutine,
|
|
|
+this parameter can be @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_rotate (lua_State *L, int idx, int n);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Rotates the stack elements between the valid index @id{idx}
|
|
|
+and the top of the stack.
|
|
|
+The elements are rotated @id{n} positions in the direction of the top,
|
|
|
+for a positive @id{n},
|
|
|
+or @T{-n} positions in the direction of the bottom,
|
|
|
+for a negative @id{n}.
|
|
|
+The absolute value of @id{n} must not be greater than the size
|
|
|
+of the slice being rotated.
|
|
|
+This function cannot be called with a pseudo-index,
|
|
|
+because a pseudo-index is not an actual stack position.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_setallocf (lua_State *L, lua_Alloc f, void *ud);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Changes the @x{allocator function} of a given state to @id{f}
|
|
|
+with user data @id{ud}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_setfield (lua_State *L, int index, const char *k);|
|
|
|
+@apii{1,0,e}
|
|
|
+
|
|
|
+Does the equivalent to @T{t[k] = v},
|
|
|
+where @id{t} is the value at the given index
|
|
|
+and @id{v} is the value at the top of the stack.
|
|
|
+
|
|
|
+This function pops the value from the stack.
|
|
|
+As in Lua, this function may trigger a metamethod
|
|
|
+for the @Q{newindex} event @see{metatable}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_setglobal (lua_State *L, const char *name);|
|
|
|
+@apii{1,0,e}
|
|
|
+
|
|
|
+Pops a value from the stack and
|
|
|
+sets it as the new value of global @id{name}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_seti (lua_State *L, int index, lua_Integer n);|
|
|
|
+@apii{1,0,e}
|
|
|
+
|
|
|
+Does the equivalent to @T{t[n] = v},
|
|
|
+where @id{t} is the value at the given index
|
|
|
+and @id{v} is the value at the top of the stack.
|
|
|
+
|
|
|
+This function pops the value from the stack.
|
|
|
+As in Lua, this function may trigger a metamethod
|
|
|
+for the @Q{newindex} event @see{metatable}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_setmetatable (lua_State *L, int index);|
|
|
|
+@apii{1,0,-}
|
|
|
+
|
|
|
+Pops a table from the stack and
|
|
|
+sets it as the new metatable for the value at the given index.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_settable (lua_State *L, int index);|
|
|
|
+@apii{2,0,e}
|
|
|
+
|
|
|
+Does the equivalent to @T{t[k] = v},
|
|
|
+where @id{t} is the value at the given index,
|
|
|
+@id{v} is the value at the top of the stack,
|
|
|
+and @id{k} is the value just below the top.
|
|
|
+
|
|
|
+This function pops both the key and the value from the stack.
|
|
|
+As in Lua, this function may trigger a metamethod
|
|
|
+for the @Q{newindex} event @see{metatable}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_settop (lua_State *L, int index);|
|
|
|
+@apii{?,?,-}
|
|
|
+
|
|
|
+Accepts any index, @N{or 0},
|
|
|
+and sets the stack top to this index.
|
|
|
+If the new top is larger than the old one,
|
|
|
+then the new elements are filled with @nil.
|
|
|
+If @id{index} @N{is 0}, then all stack elements are removed.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_setiuservalue (lua_State *L, int index, int n);|
|
|
|
+@apii{1,0,-}
|
|
|
+
|
|
|
+Pops a value from the stack and sets it as
|
|
|
+the new @id{n}-th user value associated to the
|
|
|
+full userdata at the given index.
|
|
|
+Returns 0 if the userdata does not have that value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{typedef struct lua_State lua_State;|
|
|
|
+
|
|
|
+An opaque structure that points to a thread and indirectly
|
|
|
+(through the thread) to the whole state of a Lua interpreter.
|
|
|
+The Lua library is fully reentrant:
|
|
|
+it has no global variables.
|
|
|
+All information about a state is accessible through this structure.
|
|
|
+
|
|
|
+A pointer to this structure must be passed as the first argument to
|
|
|
+every function in the library, except to @Lid{lua_newstate},
|
|
|
+which creates a Lua state from scratch.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_status (lua_State *L);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the status of the thread @id{L}.
|
|
|
+
|
|
|
+The status can be 0 (@Lid{LUA_OK}) for a normal thread,
|
|
|
+an error code if the thread finished the execution
|
|
|
+of a @Lid{lua_resume} with an error,
|
|
|
+or @defid{LUA_YIELD} if the thread is suspended.
|
|
|
+
|
|
|
+You can only call functions in threads with status @Lid{LUA_OK}.
|
|
|
+You can resume threads with status @Lid{LUA_OK}
|
|
|
+(to start a new coroutine) or @Lid{LUA_YIELD}
|
|
|
+(to resume a coroutine).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{size_t lua_stringtonumber (lua_State *L, const char *s);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Converts the zero-terminated string @id{s} to a number,
|
|
|
+pushes that number into the stack,
|
|
|
+and returns the total size of the string,
|
|
|
+that is, its length plus one.
|
|
|
+The conversion can result in an integer or a float,
|
|
|
+according to the lexical conventions of Lua @see{lexical}.
|
|
|
+The string may have leading and trailing spaces and a sign.
|
|
|
+If the string is not a valid numeral,
|
|
|
+returns 0 and pushes nothing.
|
|
|
+(Note that the result can be used as a boolean,
|
|
|
+true if the conversion succeeds.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_toboolean (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Converts the Lua value at the given index to a @N{C boolean}
|
|
|
+value (@N{0 or 1}).
|
|
|
+Like all tests in Lua,
|
|
|
+@Lid{lua_toboolean} returns true for any Lua value
|
|
|
+different from @false and @nil;
|
|
|
+otherwise it returns false.
|
|
|
+(If you want to accept only actual boolean values,
|
|
|
+use @Lid{lua_isboolean} to test the value's type.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_CFunction lua_tocfunction (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Converts a value at the given index to a @N{C function}.
|
|
|
+That value must be a @N{C function};
|
|
|
+otherwise, returns @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Integer lua_tointeger (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Equivalent to @Lid{lua_tointegerx} with @id{isnum} equal to @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Integer lua_tointegerx (lua_State *L, int index, int *isnum);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Converts the Lua value at the given index
|
|
|
+to the signed integral type @Lid{lua_Integer}.
|
|
|
+The Lua value must be an integer,
|
|
|
+or a number or string convertible to an integer @see{coercion};
|
|
|
+otherwise, @id{lua_tointegerx} @N{returns 0}.
|
|
|
+
|
|
|
+If @id{isnum} is not @id{NULL},
|
|
|
+its referent is assigned a boolean value that
|
|
|
+indicates whether the operation succeeded.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_tolstring (lua_State *L, int index, size_t *len);|
|
|
|
+@apii{0,0,m}
|
|
|
+
|
|
|
+Converts the Lua value at the given index to a @N{C string}.
|
|
|
+If @id{len} is not @id{NULL},
|
|
|
+it sets @T{*len} with the string length.
|
|
|
+The Lua value must be a string or a number;
|
|
|
+otherwise, the function returns @id{NULL}.
|
|
|
+If the value is a number,
|
|
|
+then @id{lua_tolstring} also
|
|
|
+@emph{changes the actual value in the stack to a string}.
|
|
|
+(This change confuses @Lid{lua_next}
|
|
|
+when @id{lua_tolstring} is applied to keys during a table traversal.)
|
|
|
+
|
|
|
+@id{lua_tolstring} returns a pointer
|
|
|
+to a string inside the Lua state.
|
|
|
+This string always has a zero (@Char{\0})
|
|
|
+after its last character (as @N{in C}),
|
|
|
+but can contain other zeros in its body.
|
|
|
+
|
|
|
+Because Lua has garbage collection,
|
|
|
+there is no guarantee that the pointer returned by @id{lua_tolstring}
|
|
|
+will be valid after the corresponding Lua value is removed from the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Number lua_tonumber (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Equivalent to @Lid{lua_tonumberx} with @id{isnum} equal to @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Number lua_tonumberx (lua_State *L, int index, int *isnum);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Converts the Lua value at the given index
|
|
|
+to the @N{C type} @Lid{lua_Number} @seeC{lua_Number}.
|
|
|
+The Lua value must be a number or a string convertible to a number
|
|
|
+@see{coercion};
|
|
|
+otherwise, @Lid{lua_tonumberx} @N{returns 0}.
|
|
|
+
|
|
|
+If @id{isnum} is not @id{NULL},
|
|
|
+its referent is assigned a boolean value that
|
|
|
+indicates whether the operation succeeded.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const void *lua_topointer (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Converts the value at the given index to a generic
|
|
|
+@N{C pointer} (@T{void*}).
|
|
|
+The value can be a userdata, a table, a thread, or a function;
|
|
|
+otherwise, @id{lua_topointer} returns @id{NULL}.
|
|
|
+Different objects will give different pointers.
|
|
|
+There is no way to convert the pointer back to its original value.
|
|
|
+
|
|
|
+Typically this function is used only for hashing and debug information.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_tostring (lua_State *L, int index);|
|
|
|
+@apii{0,0,m}
|
|
|
+
|
|
|
+Equivalent to @Lid{lua_tolstring} with @id{len} equal to @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_State *lua_tothread (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Converts the value at the given index to a Lua thread
|
|
|
+(represented as @T{lua_State*}).
|
|
|
+This value must be a thread;
|
|
|
+otherwise, the function returns @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void *lua_touserdata (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+If the value at the given index is a full userdata,
|
|
|
+returns its memory-block address.
|
|
|
+If the value is a light userdata,
|
|
|
+returns its pointer.
|
|
|
+Otherwise, returns @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_type (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the type of the value in the given valid index,
|
|
|
+or @id{LUA_TNONE} for a non-valid (but acceptable) index.
|
|
|
+The types returned by @Lid{lua_type} are coded by the following constants
|
|
|
+defined in @id{lua.h}:
|
|
|
+@defid{LUA_TNIL},
|
|
|
+@defid{LUA_TNUMBER},
|
|
|
+@defid{LUA_TBOOLEAN},
|
|
|
+@defid{LUA_TSTRING},
|
|
|
+@defid{LUA_TTABLE},
|
|
|
+@defid{LUA_TFUNCTION},
|
|
|
+@defid{LUA_TUSERDATA},
|
|
|
+@defid{LUA_TTHREAD},
|
|
|
+and
|
|
|
+@defid{LUA_TLIGHTUSERDATA}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_typename (lua_State *L, int tp);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the name of the type encoded by the value @id{tp},
|
|
|
+which must be one the values returned by @Lid{lua_type}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{typedef @ldots lua_Unsigned;|
|
|
|
+
|
|
|
+The unsigned version of @Lid{lua_Integer}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_upvalueindex (int i);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the pseudo-index that represents the @id{i}-th upvalue of
|
|
|
+the running function @see{c-closure}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Number lua_version (lua_State *L);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the version number of this core.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+typedef int (*lua_Writer) (lua_State *L,
|
|
|
+ const void* p,
|
|
|
+ size_t sz,
|
|
|
+ void* ud);|
|
|
|
+
|
|
|
+The type of the writer function used by @Lid{lua_dump}.
|
|
|
+Every time it produces another piece of chunk,
|
|
|
+@Lid{lua_dump} calls the writer,
|
|
|
+passing along the buffer to be written (@id{p}),
|
|
|
+its size (@id{sz}),
|
|
|
+and the @id{data} parameter supplied to @Lid{lua_dump}.
|
|
|
+
|
|
|
+The writer returns an error code:
|
|
|
+@N{0 means} no errors;
|
|
|
+any other value means an error and stops @Lid{lua_dump} from
|
|
|
+calling the writer again.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_xmove (lua_State *from, lua_State *to, int n);|
|
|
|
+@apii{?,?,-}
|
|
|
+
|
|
|
+Exchange values between different threads of the same state.
|
|
|
+
|
|
|
+This function pops @id{n} values from the stack @id{from},
|
|
|
+and pushes them onto the stack @id{to}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_yield (lua_State *L, int nresults);|
|
|
|
+@apii{?,?,v}
|
|
|
+
|
|
|
+This function is equivalent to @Lid{lua_yieldk},
|
|
|
+but it has no continuation @see{continuations}.
|
|
|
+Therefore, when the thread resumes,
|
|
|
+it continues the function that called
|
|
|
+the function calling @id{lua_yield}.
|
|
|
+To avoid surprises,
|
|
|
+this function should be called only in a tail call.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+int lua_yieldk (lua_State *L,
|
|
|
+ int nresults,
|
|
|
+ lua_KContext ctx,
|
|
|
+ lua_KFunction k);|
|
|
|
+@apii{?,?,v}
|
|
|
+
|
|
|
+Yields a coroutine (thread).
|
|
|
+
|
|
|
+When a @N{C function} calls @Lid{lua_yieldk},
|
|
|
+the running coroutine suspends its execution,
|
|
|
+and the call to @Lid{lua_resume} that started this coroutine returns.
|
|
|
+The parameter @id{nresults} is the number of values from the stack
|
|
|
+that will be passed as results to @Lid{lua_resume}.
|
|
|
+
|
|
|
+When the coroutine is resumed again,
|
|
|
+Lua calls the given @x{continuation function} @id{k} to continue
|
|
|
+the execution of the @N{C function} that yielded @see{continuations}.
|
|
|
+This continuation function receives the same stack
|
|
|
+from the previous function,
|
|
|
+with the @id{n} results removed and
|
|
|
+replaced by the arguments passed to @Lid{lua_resume}.
|
|
|
+Moreover,
|
|
|
+the continuation function receives the value @id{ctx}
|
|
|
+that was passed to @Lid{lua_yieldk}.
|
|
|
+
|
|
|
+Usually, this function does not return;
|
|
|
+when the coroutine eventually resumes,
|
|
|
+it continues executing the continuation function.
|
|
|
+However, there is one special case,
|
|
|
+which is when this function is called
|
|
|
+from inside a line or a count hook @see{debugI}.
|
|
|
+In that case, @id{lua_yieldk} should be called with no continuation
|
|
|
+(probably in the form of @Lid{lua_yield}) and no results,
|
|
|
+and the hook should return immediately after the call.
|
|
|
+Lua will yield and,
|
|
|
+when the coroutine resumes again,
|
|
|
+it will continue the normal execution
|
|
|
+of the (Lua) function that triggered the hook.
|
|
|
+
|
|
|
+This function can raise an error if it is called from a thread
|
|
|
+with a pending C call with no continuation function
|
|
|
+(what is called a @emphx{C-call boundary},
|
|
|
+or it is called from a thread that is not running inside a resume
|
|
|
+(typically the main thread).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{debugI| @title{The Debug Interface}
|
|
|
+
|
|
|
+Lua has no built-in debugging facilities.
|
|
|
+Instead, it offers a special interface
|
|
|
+by means of functions and @emph{hooks}.
|
|
|
+This interface allows the construction of different
|
|
|
+kinds of debuggers, profilers, and other tools
|
|
|
+that need @Q{inside information} from the interpreter.
|
|
|
+
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+typedef struct lua_Debug {
|
|
|
+ int event;
|
|
|
+ const char *name; /* (n) */
|
|
|
+ const char *namewhat; /* (n) */
|
|
|
+ const char *what; /* (S) */
|
|
|
+ const char *source; /* (S) */
|
|
|
+ int currentline; /* (l) */
|
|
|
+ int linedefined; /* (S) */
|
|
|
+ int lastlinedefined; /* (S) */
|
|
|
+ unsigned char nups; /* (u) number of upvalues */
|
|
|
+ unsigned char nparams; /* (u) number of parameters */
|
|
|
+ char isvararg; /* (u) */
|
|
|
+ char istailcall; /* (t) */
|
|
|
+ unsigned short ftransfer; /* (r) index of first value transferred */
|
|
|
+ unsigned short ntransfer; /* (r) number of transferred values */
|
|
|
+ char short_src[LUA_IDSIZE]; /* (S) */
|
|
|
+ /* private part */
|
|
|
+ @rep{other fields}
|
|
|
+} lua_Debug;
|
|
|
+|
|
|
|
+
|
|
|
+A structure used to carry different pieces of
|
|
|
+information about a function or an activation record.
|
|
|
+@Lid{lua_getstack} fills only the private part
|
|
|
+of this structure, for later use.
|
|
|
+To fill the other fields of @Lid{lua_Debug} with useful information,
|
|
|
+call @Lid{lua_getinfo}.
|
|
|
+
|
|
|
+The fields of @Lid{lua_Debug} have the following meaning:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@id{source}|
|
|
|
+the name of the chunk that created the function.
|
|
|
+If @T{source} starts with a @Char{@At},
|
|
|
+it means that the function was defined in a file where
|
|
|
+the file name follows the @Char{@At}.
|
|
|
+If @T{source} starts with a @Char{=},
|
|
|
+the remainder of its contents describe the source in a user-dependent manner.
|
|
|
+Otherwise,
|
|
|
+the function was defined in a string where
|
|
|
+@T{source} is that string.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{short_src}|
|
|
|
+a @Q{printable} version of @T{source}, to be used in error messages.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{linedefined}|
|
|
|
+the line number where the definition of the function starts.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{lastlinedefined}|
|
|
|
+the line number where the definition of the function ends.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{what}|
|
|
|
+the string @T{"Lua"} if the function is a Lua function,
|
|
|
+@T{"C"} if it is a @N{C function},
|
|
|
+@T{"main"} if it is the main part of a chunk.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{currentline}|
|
|
|
+the current line where the given function is executing.
|
|
|
+When no line information is available,
|
|
|
+@T{currentline} is set to @num{-1}.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{name}|
|
|
|
+a reasonable name for the given function.
|
|
|
+Because functions in Lua are first-class values,
|
|
|
+they do not have a fixed name:
|
|
|
+some functions can be the value of multiple global variables,
|
|
|
+while others can be stored only in a table field.
|
|
|
+The @T{lua_getinfo} function checks how the function was
|
|
|
+called to find a suitable name.
|
|
|
+If it cannot find a name,
|
|
|
+then @id{name} is set to @id{NULL}.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{namewhat}|
|
|
|
+explains the @T{name} field.
|
|
|
+The value of @T{namewhat} can be
|
|
|
+@T{"global"}, @T{"local"}, @T{"method"},
|
|
|
+@T{"field"}, @T{"upvalue"}, or @T{""} (the empty string),
|
|
|
+according to how the function was called.
|
|
|
+(Lua uses the empty string when no other option seems to apply.)
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{istailcall}|
|
|
|
+true if this function invocation was called by a tail call.
|
|
|
+In this case, the caller of this level is not in the stack.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{nups}|
|
|
|
+the number of upvalues of the function.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{nparams}|
|
|
|
+the number of parameters of the function
|
|
|
+(always @N{0 for} @N{C functions}).
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{isvararg}|
|
|
|
+true if the function is a vararg function
|
|
|
+(always true for @N{C functions}).
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{ftransfer}|
|
|
|
+the index on the stack of the first value being @Q{transferred},
|
|
|
+that is, parameters in a call or return values in a return.
|
|
|
+(The other values are in consecutive indices.)
|
|
|
+Using this index, you can access and modify these values
|
|
|
+through @Lid{lua_getlocal} and @Lid{lua_setlocal}.
|
|
|
+This field is only meaningful during a
|
|
|
+call hook, denoting the first parameter,
|
|
|
+or a return hook, denoting the first value being returned.
|
|
|
+(For call hooks, this value is always 1.)
|
|
|
+}
|
|
|
+
|
|
|
+@item{@id{ntransfer}|
|
|
|
+The number of values being transferred (see previous item).
|
|
|
+(For calls of Lua functions,
|
|
|
+this value is always equal to @id{nparams}.)
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Hook lua_gethook (lua_State *L);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the current hook function.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_gethookcount (lua_State *L);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the current hook count.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_gethookmask (lua_State *L);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the current hook mask.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar);|
|
|
|
+@apii{0|1,0|1|2,m}
|
|
|
+
|
|
|
+Gets information about a specific function or function invocation.
|
|
|
+
|
|
|
+To get information about a function invocation,
|
|
|
+the parameter @id{ar} must be a valid activation record that was
|
|
|
+filled by a previous call to @Lid{lua_getstack} or
|
|
|
+given as argument to a hook @seeC{lua_Hook}.
|
|
|
+
|
|
|
+To get information about a function, you push it onto the stack
|
|
|
+and start the @id{what} string with the character @Char{>}.
|
|
|
+(In that case,
|
|
|
+@id{lua_getinfo} pops the function from the top of the stack.)
|
|
|
+For instance, to know in which line a function @id{f} was defined,
|
|
|
+you can write the following code:
|
|
|
+@verbatim{
|
|
|
+lua_Debug ar;
|
|
|
+lua_getglobal(L, "f"); /* get global 'f' */
|
|
|
+lua_getinfo(L, ">S", &ar);
|
|
|
+printf("%d\n", ar.linedefined);
|
|
|
+}
|
|
|
+
|
|
|
+Each character in the string @id{what}
|
|
|
+selects some fields of the structure @id{ar} to be filled or
|
|
|
+a value to be pushed on the stack:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@Char{n}| fills in the field @id{name} and @id{namewhat};
|
|
|
+}
|
|
|
+
|
|
|
+@item{@Char{S}|
|
|
|
+fills in the fields @id{source}, @id{short_src},
|
|
|
+@id{linedefined}, @id{lastlinedefined}, and @id{what};
|
|
|
+}
|
|
|
+
|
|
|
+@item{@Char{l}| fills in the field @id{currentline};
|
|
|
+}
|
|
|
+
|
|
|
+@item{@Char{t}| fills in the field @id{istailcall};
|
|
|
+}
|
|
|
+
|
|
|
+@item{@Char{u}| fills in the fields
|
|
|
+@id{nups}, @id{nparams}, and @id{isvararg};
|
|
|
+}
|
|
|
+
|
|
|
+@item{@Char{f}|
|
|
|
+pushes onto the stack the function that is
|
|
|
+running at the given level;
|
|
|
+}
|
|
|
+
|
|
|
+@item{@Char{L}|
|
|
|
+pushes onto the stack a table whose indices are the
|
|
|
+numbers of the lines that are valid on the function.
|
|
|
+(A @emph{valid line} is a line with some associated code,
|
|
|
+that is, a line where you can put a break point.
|
|
|
+Non-valid lines include empty lines and comments.)
|
|
|
+
|
|
|
+If this option is given together with option @Char{f},
|
|
|
+its table is pushed after the function.
|
|
|
+
|
|
|
+This is the only option that can raise a memory error.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+This function returns 0 if given an invalid option in @id{what}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n);|
|
|
|
+@apii{0,0|1,-}
|
|
|
+
|
|
|
+Gets information about a local variable or a temporary value
|
|
|
+of a given activation record or a given function.
|
|
|
+
|
|
|
+In the first case,
|
|
|
+the parameter @id{ar} must be a valid activation record that was
|
|
|
+filled by a previous call to @Lid{lua_getstack} or
|
|
|
+given as argument to a hook @seeC{lua_Hook}.
|
|
|
+The index @id{n} selects which local variable to inspect;
|
|
|
+see @Lid{debug.getlocal} for details about variable indices
|
|
|
+and names.
|
|
|
+
|
|
|
+@Lid{lua_getlocal} pushes the variable's value onto the stack
|
|
|
+and returns its name.
|
|
|
+
|
|
|
+In the second case, @id{ar} must be @id{NULL} and the function
|
|
|
+to be inspected must be at the top of the stack.
|
|
|
+In this case, only parameters of Lua functions are visible
|
|
|
+(as there is no information about what variables are active)
|
|
|
+and no values are pushed onto the stack.
|
|
|
+
|
|
|
+Returns @id{NULL} (and pushes nothing)
|
|
|
+when the index is greater than
|
|
|
+the number of active local variables.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int lua_getstack (lua_State *L, int level, lua_Debug *ar);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Gets information about the interpreter runtime stack.
|
|
|
+
|
|
|
+This function fills parts of a @Lid{lua_Debug} structure with
|
|
|
+an identification of the @emph{activation record}
|
|
|
+of the function executing at a given level.
|
|
|
+@N{Level 0} is the current running function,
|
|
|
+whereas level @M{n+1} is the function that has called level @M{n}
|
|
|
+(except for tail calls, which do not count on the stack).
|
|
|
+When there are no errors, @Lid{lua_getstack} returns 1;
|
|
|
+when called with a level greater than the stack depth,
|
|
|
+it returns 0.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_getupvalue (lua_State *L, int funcindex, int n);|
|
|
|
+@apii{0,0|1,-}
|
|
|
+
|
|
|
+Gets information about the @id{n}-th upvalue
|
|
|
+of the closure at index @id{funcindex}.
|
|
|
+It pushes the upvalue's value onto the stack
|
|
|
+and returns its name.
|
|
|
+Returns @id{NULL} (and pushes nothing)
|
|
|
+when the index @id{n} is greater than the number of upvalues.
|
|
|
+
|
|
|
+For @N{C functions}, this function uses the empty string @T{""}
|
|
|
+as a name for all upvalues.
|
|
|
+(For Lua functions,
|
|
|
+upvalues are the external local variables that the function uses,
|
|
|
+and that are consequently included in its closure.)
|
|
|
+
|
|
|
+Upvalues have no particular order,
|
|
|
+as they are active through the whole function.
|
|
|
+They are numbered in an arbitrary order.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);|
|
|
|
+
|
|
|
+Type for debugging hook functions.
|
|
|
+
|
|
|
+Whenever a hook is called, its @id{ar} argument has its field
|
|
|
+@id{event} set to the specific event that triggered the hook.
|
|
|
+Lua identifies these events with the following constants:
|
|
|
+@defid{LUA_HOOKCALL}, @defid{LUA_HOOKRET},
|
|
|
+@defid{LUA_HOOKTAILCALL}, @defid{LUA_HOOKLINE},
|
|
|
+and @defid{LUA_HOOKCOUNT}.
|
|
|
+Moreover, for line events, the field @id{currentline} is also set.
|
|
|
+To get the value of any other field in @id{ar},
|
|
|
+the hook must call @Lid{lua_getinfo}.
|
|
|
+
|
|
|
+For call events, @id{event} can be @id{LUA_HOOKCALL},
|
|
|
+the normal value, or @id{LUA_HOOKTAILCALL}, for a tail call;
|
|
|
+in this case, there will be no corresponding return event.
|
|
|
+
|
|
|
+While Lua is running a hook, it disables other calls to hooks.
|
|
|
+Therefore, if a hook calls back Lua to execute a function or a chunk,
|
|
|
+this execution occurs without any calls to hooks.
|
|
|
+
|
|
|
+Hook functions cannot have continuations,
|
|
|
+that is, they cannot call @Lid{lua_yieldk},
|
|
|
+@Lid{lua_pcallk}, or @Lid{lua_callk} with a non-null @id{k}.
|
|
|
+
|
|
|
+Hook functions can yield under the following conditions:
|
|
|
+Only count and line events can yield;
|
|
|
+to yield, a hook function must finish its execution
|
|
|
+calling @Lid{lua_yield} with @id{nresults} equal to zero
|
|
|
+(that is, with no values).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void lua_sethook (lua_State *L, lua_Hook f, int mask, int count);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Sets the debugging hook function.
|
|
|
+
|
|
|
+Argument @id{f} is the hook function.
|
|
|
+@id{mask} specifies on which events the hook will be called:
|
|
|
+it is formed by a bitwise OR of the constants
|
|
|
+@defid{LUA_MASKCALL},
|
|
|
+@defid{LUA_MASKRET},
|
|
|
+@defid{LUA_MASKLINE},
|
|
|
+and @defid{LUA_MASKCOUNT}.
|
|
|
+The @id{count} argument is only meaningful when the mask
|
|
|
+includes @id{LUA_MASKCOUNT}.
|
|
|
+For each event, the hook is called as explained below:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{The call hook| is called when the interpreter calls a function.
|
|
|
+The hook is called just after Lua enters the new function,
|
|
|
+before the function gets its arguments.
|
|
|
+}
|
|
|
+
|
|
|
+@item{The return hook| is called when the interpreter returns from a function.
|
|
|
+The hook is called just before Lua leaves the function.
|
|
|
+There is no standard way to access the values
|
|
|
+to be returned by the function.
|
|
|
+}
|
|
|
+
|
|
|
+@item{The line hook| is called when the interpreter is about to
|
|
|
+start the execution of a new line of code,
|
|
|
+or when it jumps back in the code (even to the same line).
|
|
|
+(This event only happens while Lua is executing a Lua function.)
|
|
|
+}
|
|
|
+
|
|
|
+@item{The count hook| is called after the interpreter executes every
|
|
|
+@T{count} instructions.
|
|
|
+(This event only happens while Lua is executing a Lua function.)
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+A hook is disabled by setting @id{mask} to zero.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n);|
|
|
|
+@apii{0|1,0,-}
|
|
|
+
|
|
|
+Sets the value of a local variable of a given activation record.
|
|
|
+It assigns the value at the top of the stack
|
|
|
+to the variable and returns its name.
|
|
|
+It also pops the value from the stack.
|
|
|
+
|
|
|
+Returns @id{NULL} (and pops nothing)
|
|
|
+when the index is greater than
|
|
|
+the number of active local variables.
|
|
|
+
|
|
|
+Parameters @id{ar} and @id{n} are as in function @Lid{lua_getlocal}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *lua_setupvalue (lua_State *L, int funcindex, int n);|
|
|
|
+@apii{0|1,0,-}
|
|
|
+
|
|
|
+Sets the value of a closure's upvalue.
|
|
|
+It assigns the value at the top of the stack
|
|
|
+to the upvalue and returns its name.
|
|
|
+It also pops the value from the stack.
|
|
|
+
|
|
|
+Returns @id{NULL} (and pops nothing)
|
|
|
+when the index @id{n} is greater than the number of upvalues.
|
|
|
+
|
|
|
+Parameters @id{funcindex} and @id{n} are as in function @Lid{lua_getupvalue}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void *lua_upvalueid (lua_State *L, int funcindex, int n);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns a unique identifier for the upvalue numbered @id{n}
|
|
|
+from the closure at index @id{funcindex}.
|
|
|
+
|
|
|
+These unique identifiers allow a program to check whether different
|
|
|
+closures share upvalues.
|
|
|
+Lua closures that share an upvalue
|
|
|
+(that is, that access a same external local variable)
|
|
|
+will return identical ids for those upvalue indices.
|
|
|
+
|
|
|
+Parameters @id{funcindex} and @id{n} are as in function @Lid{lua_getupvalue},
|
|
|
+but @id{n} cannot be greater than the number of upvalues.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+void lua_upvaluejoin (lua_State *L, int funcindex1, int n1,
|
|
|
+ int funcindex2, int n2);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Make the @id{n1}-th upvalue of the Lua closure at index @id{funcindex1}
|
|
|
+refer to the @id{n2}-th upvalue of the Lua closure at index @id{funcindex2}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@C{-------------------------------------------------------------------------}
|
|
|
+@sect1{@title{The Auxiliary Library}
|
|
|
+
|
|
|
+@index{lauxlib.h}
|
|
|
+The @def{auxiliary library} provides several convenient functions
|
|
|
+to interface C with Lua.
|
|
|
+While the basic API provides the primitive functions for all
|
|
|
+interactions between C and Lua,
|
|
|
+the auxiliary library provides higher-level functions for some
|
|
|
+common tasks.
|
|
|
+
|
|
|
+All functions and types from the auxiliary library
|
|
|
+are defined in header file @id{lauxlib.h} and
|
|
|
+have a prefix @id{luaL_}.
|
|
|
+
|
|
|
+All functions in the auxiliary library are built on
|
|
|
+top of the basic API,
|
|
|
+and so they provide nothing that cannot be done with that API.
|
|
|
+Nevertheless, the use of the auxiliary library ensures
|
|
|
+more consistency to your code.
|
|
|
+
|
|
|
+
|
|
|
+Several functions in the auxiliary library use internally some
|
|
|
+extra stack slots.
|
|
|
+When a function in the auxiliary library uses less than five slots,
|
|
|
+it does not check the stack size;
|
|
|
+it simply assumes that there are enough slots.
|
|
|
+
|
|
|
+Several functions in the auxiliary library are used to
|
|
|
+check @N{C function} arguments.
|
|
|
+Because the error message is formatted for arguments
|
|
|
+(e.g., @St{bad argument #1}),
|
|
|
+you should not use these functions for other stack values.
|
|
|
+
|
|
|
+Functions called @id{luaL_check*}
|
|
|
+always raise an error if the check is not satisfied.
|
|
|
+
|
|
|
+@sect2{@title{Functions and Types}
|
|
|
+
|
|
|
+Here we list all functions and types from the auxiliary library
|
|
|
+in alphabetical order.
|
|
|
+
|
|
|
+
|
|
|
+@APIEntry{void luaL_addchar (luaL_Buffer *B, char c);|
|
|
|
+@apii{?,?,m}
|
|
|
+
|
|
|
+Adds the byte @id{c} to the buffer @id{B}
|
|
|
+@seeC{luaL_Buffer}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l);|
|
|
|
+@apii{?,?,m}
|
|
|
+
|
|
|
+Adds the string pointed to by @id{s} with length @id{l} to
|
|
|
+the buffer @id{B}
|
|
|
+@seeC{luaL_Buffer}.
|
|
|
+The string can contain @x{embedded zeros}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_addsize (luaL_Buffer *B, size_t n);|
|
|
|
+@apii{?,?,-}
|
|
|
+
|
|
|
+Adds to the buffer @id{B} @seeC{luaL_Buffer}
|
|
|
+a string of length @id{n} previously copied to the
|
|
|
+buffer area @seeC{luaL_prepbuffer}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_addstring (luaL_Buffer *B, const char *s);|
|
|
|
+@apii{?,?,m}
|
|
|
+
|
|
|
+Adds the zero-terminated string pointed to by @id{s}
|
|
|
+to the buffer @id{B}
|
|
|
+@seeC{luaL_Buffer}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_addvalue (luaL_Buffer *B);|
|
|
|
+@apii{1,?,m}
|
|
|
+
|
|
|
+Adds the value at the top of the stack
|
|
|
+to the buffer @id{B}
|
|
|
+@seeC{luaL_Buffer}.
|
|
|
+Pops the value.
|
|
|
+
|
|
|
+This is the only function on string buffers that can (and must)
|
|
|
+be called with an extra element on the stack,
|
|
|
+which is the value to be added to the buffer.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+void luaL_argcheck (lua_State *L,
|
|
|
+ int cond,
|
|
|
+ int arg,
|
|
|
+ const char *extramsg);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether @id{cond} is true.
|
|
|
+If it is not, raises an error with a standard message @seeF{luaL_argerror}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_argerror (lua_State *L, int arg, const char *extramsg);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Raises an error reporting a problem with argument @id{arg}
|
|
|
+of the @N{C function} that called it,
|
|
|
+using a standard message
|
|
|
+that includes @id{extramsg} as a comment:
|
|
|
+@verbatim{
|
|
|
+bad argument #@rep{arg} to '@rep{funcname}' (@rep{extramsg})
|
|
|
+}
|
|
|
+This function never returns.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{typedef struct luaL_Buffer luaL_Buffer;|
|
|
|
+
|
|
|
+Type for a @def{string buffer}.
|
|
|
+
|
|
|
+A string buffer allows @N{C code} to build Lua strings piecemeal.
|
|
|
+Its pattern of use is as follows:
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{First declare a variable @id{b} of type @Lid{luaL_Buffer}.}
|
|
|
+
|
|
|
+@item{Then initialize it with a call @T{luaL_buffinit(L, &b)}.}
|
|
|
+
|
|
|
+@item{
|
|
|
+Then add string pieces to the buffer calling any of
|
|
|
+the @id{luaL_add*} functions.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+Finish by calling @T{luaL_pushresult(&b)}.
|
|
|
+This call leaves the final string on the top of the stack.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+If you know beforehand the total size of the resulting string,
|
|
|
+you can use the buffer like this:
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{First declare a variable @id{b} of type @Lid{luaL_Buffer}.}
|
|
|
+
|
|
|
+@item{Then initialize it and preallocate a space of
|
|
|
+size @id{sz} with a call @T{luaL_buffinitsize(L, &b, sz)}.}
|
|
|
+
|
|
|
+@item{Then produce the string into that space.}
|
|
|
+
|
|
|
+@item{
|
|
|
+Finish by calling @T{luaL_pushresultsize(&b, sz)},
|
|
|
+where @id{sz} is the total size of the resulting string
|
|
|
+copied into that space.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+During its normal operation,
|
|
|
+a string buffer uses a variable number of stack slots.
|
|
|
+So, while using a buffer, you cannot assume that you know where
|
|
|
+the top of the stack is.
|
|
|
+You can use the stack between successive calls to buffer operations
|
|
|
+as long as that use is balanced;
|
|
|
+that is,
|
|
|
+when you call a buffer operation,
|
|
|
+the stack is at the same level
|
|
|
+it was immediately after the previous buffer operation.
|
|
|
+(The only exception to this rule is @Lid{luaL_addvalue}.)
|
|
|
+After calling @Lid{luaL_pushresult} the stack is back to its
|
|
|
+level when the buffer was initialized,
|
|
|
+plus the final string on its top.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_buffinit (lua_State *L, luaL_Buffer *B);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Initializes a buffer @id{B}.
|
|
|
+This function does not allocate any space;
|
|
|
+the buffer must be declared as a variable
|
|
|
+@seeC{luaL_Buffer}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz);|
|
|
|
+@apii{?,?,m}
|
|
|
+
|
|
|
+Equivalent to the sequence
|
|
|
+@Lid{luaL_buffinit}, @Lid{luaL_prepbuffsize}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_callmeta (lua_State *L, int obj, const char *e);|
|
|
|
+@apii{0,0|1,e}
|
|
|
+
|
|
|
+Calls a metamethod.
|
|
|
+
|
|
|
+If the object at index @id{obj} has a metatable and this
|
|
|
+metatable has a field @id{e},
|
|
|
+this function calls this field passing the object as its only argument.
|
|
|
+In this case this function returns true and pushes onto the
|
|
|
+stack the value returned by the call.
|
|
|
+If there is no metatable or no metamethod,
|
|
|
+this function returns false (without pushing any value on the stack).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_checkany (lua_State *L, int arg);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether the function has an argument
|
|
|
+of any type (including @nil) at position @id{arg}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Integer luaL_checkinteger (lua_State *L, int arg);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether the function argument @id{arg} is an integer
|
|
|
+(or can be converted to an integer)
|
|
|
+and returns this integer cast to a @Lid{lua_Integer}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *luaL_checklstring (lua_State *L, int arg, size_t *l);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether the function argument @id{arg} is a string
|
|
|
+and returns this string;
|
|
|
+if @id{l} is not @id{NULL} fills @T{*l}
|
|
|
+with the string's length.
|
|
|
+
|
|
|
+This function uses @Lid{lua_tolstring} to get its result,
|
|
|
+so all conversions and caveats of that function apply here.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Number luaL_checknumber (lua_State *L, int arg);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether the function argument @id{arg} is a number
|
|
|
+and returns this number.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+int luaL_checkoption (lua_State *L,
|
|
|
+ int arg,
|
|
|
+ const char *def,
|
|
|
+ const char *const lst[]);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether the function argument @id{arg} is a string and
|
|
|
+searches for this string in the array @id{lst}
|
|
|
+(which must be NULL-terminated).
|
|
|
+Returns the index in the array where the string was found.
|
|
|
+Raises an error if the argument is not a string or
|
|
|
+if the string cannot be found.
|
|
|
+
|
|
|
+If @id{def} is not @id{NULL},
|
|
|
+the function uses @id{def} as a default value when
|
|
|
+there is no argument @id{arg} or when this argument is @nil.
|
|
|
+
|
|
|
+This is a useful function for mapping strings to @N{C enums}.
|
|
|
+(The usual convention in Lua libraries is
|
|
|
+to use strings instead of numbers to select options.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_checkstack (lua_State *L, int sz, const char *msg);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Grows the stack size to @T{top + sz} elements,
|
|
|
+raising an error if the stack cannot grow to that size.
|
|
|
+@id{msg} is an additional text to go into the error message
|
|
|
+(or @id{NULL} for no additional text).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *luaL_checkstring (lua_State *L, int arg);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether the function argument @id{arg} is a string
|
|
|
+and returns this string.
|
|
|
+
|
|
|
+This function uses @Lid{lua_tolstring} to get its result,
|
|
|
+so all conversions and caveats of that function apply here.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_checktype (lua_State *L, int arg, int t);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether the function argument @id{arg} has type @id{t}.
|
|
|
+See @Lid{lua_type} for the encoding of types for @id{t}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void *luaL_checkudata (lua_State *L, int arg, const char *tname);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether the function argument @id{arg} is a userdata
|
|
|
+of the type @id{tname} @seeC{luaL_newmetatable} and
|
|
|
+returns the userdata's memory-block address @seeC{lua_touserdata}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_checkversion (lua_State *L);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Checks whether the code making the call and the Lua library being called
|
|
|
+are using the same version of Lua and the same numeric types.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_dofile (lua_State *L, const char *filename);|
|
|
|
+@apii{0,?,m}
|
|
|
+
|
|
|
+Loads and runs the given file.
|
|
|
+It is defined as the following macro:
|
|
|
+@verbatim{
|
|
|
+(luaL_loadfile(L, filename) || lua_pcall(L, 0, LUA_MULTRET, 0))
|
|
|
+}
|
|
|
+It returns false if there are no errors
|
|
|
+or true in case of errors.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_dostring (lua_State *L, const char *str);|
|
|
|
+@apii{0,?,-}
|
|
|
+
|
|
|
+Loads and runs the given string.
|
|
|
+It is defined as the following macro:
|
|
|
+@verbatim{
|
|
|
+(luaL_loadstring(L, str) || lua_pcall(L, 0, LUA_MULTRET, 0))
|
|
|
+}
|
|
|
+It returns false if there are no errors
|
|
|
+or true in case of errors.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_error (lua_State *L, const char *fmt, ...);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+Raises an error.
|
|
|
+The error message format is given by @id{fmt}
|
|
|
+plus any extra arguments,
|
|
|
+following the same rules of @Lid{lua_pushfstring}.
|
|
|
+It also adds at the beginning of the message the file name and
|
|
|
+the line number where the error occurred,
|
|
|
+if this information is available.
|
|
|
+
|
|
|
+This function never returns,
|
|
|
+but it is an idiom to use it in @N{C functions}
|
|
|
+as @T{return luaL_error(@rep{args})}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_execresult (lua_State *L, int stat);|
|
|
|
+@apii{0,3,m}
|
|
|
+
|
|
|
+This function produces the return values for
|
|
|
+process-related functions in the standard library
|
|
|
+(@Lid{os.execute} and @Lid{io.close}).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+int luaL_fileresult (lua_State *L, int stat, const char *fname);|
|
|
|
+@apii{0,1|3,m}
|
|
|
+
|
|
|
+This function produces the return values for
|
|
|
+file-related functions in the standard library
|
|
|
+(@Lid{io.open}, @Lid{os.rename}, @Lid{file:seek}, etc.).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_getmetafield (lua_State *L, int obj, const char *e);|
|
|
|
+@apii{0,0|1,m}
|
|
|
+
|
|
|
+Pushes onto the stack the field @id{e} from the metatable
|
|
|
+of the object at index @id{obj} and returns the type of the pushed value.
|
|
|
+If the object does not have a metatable,
|
|
|
+or if the metatable does not have this field,
|
|
|
+pushes nothing and returns @id{LUA_TNIL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_getmetatable (lua_State *L, const char *tname);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Pushes onto the stack the metatable associated with the name @id{tname}
|
|
|
+in the registry @seeC{luaL_newmetatable},
|
|
|
+or @nil if there is no metatable associated with that name.
|
|
|
+Returns the type of the pushed value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_getsubtable (lua_State *L, int idx, const char *fname);|
|
|
|
+@apii{0,1,e}
|
|
|
+
|
|
|
+Ensures that the value @T{t[fname]},
|
|
|
+where @id{t} is the value at index @id{idx},
|
|
|
+is a table,
|
|
|
+and pushes that table onto the stack.
|
|
|
+Returns true if it finds a previous table there
|
|
|
+and false if it creates a new table.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+const char *luaL_gsub (lua_State *L,
|
|
|
+ const char *s,
|
|
|
+ const char *p,
|
|
|
+ const char *r);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Creates a copy of string @id{s} by replacing
|
|
|
+any occurrence of the string @id{p}
|
|
|
+with the string @id{r}.
|
|
|
+Pushes the resulting string on the stack and returns it.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Integer luaL_len (lua_State *L, int index);|
|
|
|
+@apii{0,0,e}
|
|
|
+
|
|
|
+Returns the @Q{length} of the value at the given index
|
|
|
+as a number;
|
|
|
+it is equivalent to the @Char{#} operator in Lua @see{len-op}.
|
|
|
+Raises an error if the result of the operation is not an integer.
|
|
|
+(This case only can happen through metamethods.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+int luaL_loadbuffer (lua_State *L,
|
|
|
+ const char *buff,
|
|
|
+ size_t sz,
|
|
|
+ const char *name);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Equivalent to @Lid{luaL_loadbufferx} with @id{mode} equal to @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+int luaL_loadbufferx (lua_State *L,
|
|
|
+ const char *buff,
|
|
|
+ size_t sz,
|
|
|
+ const char *name,
|
|
|
+ const char *mode);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Loads a buffer as a Lua chunk.
|
|
|
+This function uses @Lid{lua_load} to load the chunk in the
|
|
|
+buffer pointed to by @id{buff} with size @id{sz}.
|
|
|
+
|
|
|
+This function returns the same results as @Lid{lua_load}.
|
|
|
+@id{name} is the chunk name,
|
|
|
+used for debug information and error messages.
|
|
|
+The string @id{mode} works as in function @Lid{lua_load}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@APIEntry{int luaL_loadfile (lua_State *L, const char *filename);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Equivalent to @Lid{luaL_loadfilex} with @id{mode} equal to @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_loadfilex (lua_State *L, const char *filename,
|
|
|
+ const char *mode);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Loads a file as a Lua chunk.
|
|
|
+This function uses @Lid{lua_load} to load the chunk in the file
|
|
|
+named @id{filename}.
|
|
|
+If @id{filename} is @id{NULL},
|
|
|
+then it loads from the standard input.
|
|
|
+The first line in the file is ignored if it starts with a @T{#}.
|
|
|
+
|
|
|
+The string @id{mode} works as in function @Lid{lua_load}.
|
|
|
+
|
|
|
+This function returns the same results as @Lid{lua_load},
|
|
|
+but it has an extra error code @defid{LUA_ERRFILE}
|
|
|
+for file-related errors
|
|
|
+(e.g., it cannot open or read the file).
|
|
|
+
|
|
|
+As @Lid{lua_load}, this function only loads the chunk;
|
|
|
+it does not run it.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_loadstring (lua_State *L, const char *s);|
|
|
|
+@apii{0,1,-}
|
|
|
+
|
|
|
+Loads a string as a Lua chunk.
|
|
|
+This function uses @Lid{lua_load} to load the chunk in
|
|
|
+the zero-terminated string @id{s}.
|
|
|
+
|
|
|
+This function returns the same results as @Lid{lua_load}.
|
|
|
+
|
|
|
+Also as @Lid{lua_load}, this function only loads the chunk;
|
|
|
+it does not run it.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@APIEntry{void luaL_newlib (lua_State *L, const luaL_Reg l[]);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Creates a new table and registers there
|
|
|
+the functions in list @id{l}.
|
|
|
+
|
|
|
+It is implemented as the following macro:
|
|
|
+@verbatim{
|
|
|
+(luaL_newlibtable(L,l), luaL_setfuncs(L,l,0))
|
|
|
+}
|
|
|
+The array @id{l} must be the actual array,
|
|
|
+not a pointer to it.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_newlibtable (lua_State *L, const luaL_Reg l[]);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Creates a new table with a size optimized
|
|
|
+to store all entries in the array @id{l}
|
|
|
+(but does not actually store them).
|
|
|
+It is intended to be used in conjunction with @Lid{luaL_setfuncs}
|
|
|
+@seeF{luaL_newlib}.
|
|
|
+
|
|
|
+It is implemented as a macro.
|
|
|
+The array @id{l} must be the actual array,
|
|
|
+not a pointer to it.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_newmetatable (lua_State *L, const char *tname);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+If the registry already has the key @id{tname},
|
|
|
+returns 0.
|
|
|
+Otherwise,
|
|
|
+creates a new table to be used as a metatable for userdata,
|
|
|
+adds to this new table the pair @T{__name = tname},
|
|
|
+adds to the registry the pair @T{[tname] = new table},
|
|
|
+and returns 1.
|
|
|
+(The entry @idx{__name} is used by some error-reporting functions.)
|
|
|
+
|
|
|
+In both cases pushes onto the stack the final value associated
|
|
|
+with @id{tname} in the registry.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_State *luaL_newstate (void);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Creates a new Lua state.
|
|
|
+It calls @Lid{lua_newstate} with an
|
|
|
+allocator based on the @N{standard C} @id{realloc} function
|
|
|
+and then sets a panic function @see{C-error} that prints
|
|
|
+an error message to the standard error output in case of fatal
|
|
|
+errors.
|
|
|
+
|
|
|
+Returns the new state,
|
|
|
+or @id{NULL} if there is a @x{memory allocation error}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_openlibs (lua_State *L);|
|
|
|
+@apii{0,0,e}
|
|
|
+
|
|
|
+Opens all standard Lua libraries into the given state.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+T luaL_opt (L, func, arg, dflt);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+This macro is defined as follows:
|
|
|
+@verbatim{
|
|
|
+(lua_isnoneornil(L,(arg)) ? (dflt) : func(L,(arg)))
|
|
|
+}
|
|
|
+In words, if the argument @id{arg} is nil or absent,
|
|
|
+the macro results in the default @id{dflt}.
|
|
|
+Otherwise, it results in the result of calling @id{func}
|
|
|
+with the state @id{L} and the argument index @id{arg} as
|
|
|
+parameters.
|
|
|
+Note that it evaluates the expression @id{dflt} only if needed.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+lua_Integer luaL_optinteger (lua_State *L,
|
|
|
+ int arg,
|
|
|
+ lua_Integer d);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+If the function argument @id{arg} is an integer
|
|
|
+(or convertible to an integer),
|
|
|
+returns this integer.
|
|
|
+If this argument is absent or is @nil,
|
|
|
+returns @id{d}.
|
|
|
+Otherwise, raises an error.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+const char *luaL_optlstring (lua_State *L,
|
|
|
+ int arg,
|
|
|
+ const char *d,
|
|
|
+ size_t *l);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+If the function argument @id{arg} is a string,
|
|
|
+returns this string.
|
|
|
+If this argument is absent or is @nil,
|
|
|
+returns @id{d}.
|
|
|
+Otherwise, raises an error.
|
|
|
+
|
|
|
+If @id{l} is not @id{NULL},
|
|
|
+fills the position @T{*l} with the result's length.
|
|
|
+If the result is @id{NULL}
|
|
|
+(only possible when returning @id{d} and @T{d == NULL}),
|
|
|
+its length is considered zero.
|
|
|
+
|
|
|
+This function uses @Lid{lua_tolstring} to get its result,
|
|
|
+so all conversions and caveats of that function apply here.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{lua_Number luaL_optnumber (lua_State *L, int arg, lua_Number d);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+If the function argument @id{arg} is a number,
|
|
|
+returns this number.
|
|
|
+If this argument is absent or is @nil,
|
|
|
+returns @id{d}.
|
|
|
+Otherwise, raises an error.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+const char *luaL_optstring (lua_State *L,
|
|
|
+ int arg,
|
|
|
+ const char *d);|
|
|
|
+@apii{0,0,v}
|
|
|
+
|
|
|
+If the function argument @id{arg} is a string,
|
|
|
+returns this string.
|
|
|
+If this argument is absent or is @nil,
|
|
|
+returns @id{d}.
|
|
|
+Otherwise, raises an error.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{char *luaL_prepbuffer (luaL_Buffer *B);|
|
|
|
+@apii{?,?,m}
|
|
|
+
|
|
|
+Equivalent to @Lid{luaL_prepbuffsize}
|
|
|
+with the predefined size @defid{LUAL_BUFFERSIZE}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{char *luaL_prepbuffsize (luaL_Buffer *B, size_t sz);|
|
|
|
+@apii{?,?,m}
|
|
|
+
|
|
|
+Returns an address to a space of size @id{sz}
|
|
|
+where you can copy a string to be added to buffer @id{B}
|
|
|
+@seeC{luaL_Buffer}.
|
|
|
+After copying the string into this space you must call
|
|
|
+@Lid{luaL_addsize} with the size of the string to actually add
|
|
|
+it to the buffer.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_pushresult (luaL_Buffer *B);|
|
|
|
+@apii{?,1,m}
|
|
|
+
|
|
|
+Finishes the use of buffer @id{B} leaving the final string on
|
|
|
+the top of the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_pushresultsize (luaL_Buffer *B, size_t sz);|
|
|
|
+@apii{?,1,m}
|
|
|
+
|
|
|
+Equivalent to the sequence @Lid{luaL_addsize}, @Lid{luaL_pushresult}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{int luaL_ref (lua_State *L, int t);|
|
|
|
+@apii{1,0,m}
|
|
|
+
|
|
|
+Creates and returns a @def{reference},
|
|
|
+in the table at index @id{t},
|
|
|
+for the object at the top of the stack (and pops the object).
|
|
|
+
|
|
|
+A reference is a unique integer key.
|
|
|
+As long as you do not manually add integer keys into table @id{t},
|
|
|
+@Lid{luaL_ref} ensures the uniqueness of the key it returns.
|
|
|
+You can retrieve an object referred by reference @id{r}
|
|
|
+by calling @T{lua_rawgeti(L, t, r)}.
|
|
|
+Function @Lid{luaL_unref} frees a reference and its associated object.
|
|
|
+
|
|
|
+If the object at the top of the stack is @nil,
|
|
|
+@Lid{luaL_ref} returns the constant @defid{LUA_REFNIL}.
|
|
|
+The constant @defid{LUA_NOREF} is guaranteed to be different
|
|
|
+from any reference returned by @Lid{luaL_ref}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+typedef struct luaL_Reg {
|
|
|
+ const char *name;
|
|
|
+ lua_CFunction func;
|
|
|
+} luaL_Reg;
|
|
|
+|
|
|
|
+
|
|
|
+Type for arrays of functions to be registered by
|
|
|
+@Lid{luaL_setfuncs}.
|
|
|
+@id{name} is the function name and @id{func} is a pointer to
|
|
|
+the function.
|
|
|
+Any array of @Lid{luaL_Reg} must end with a sentinel entry
|
|
|
+in which both @id{name} and @id{func} are @id{NULL}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+void luaL_requiref (lua_State *L, const char *modname,
|
|
|
+ lua_CFunction openf, int glb);|
|
|
|
+@apii{0,1,e}
|
|
|
+
|
|
|
+If @T{package.loaded[modname]} is not true,
|
|
|
+calls function @id{openf} with string @id{modname} as an argument
|
|
|
+and sets the call result to @T{package.loaded[modname]},
|
|
|
+as if that function has been called through @Lid{require}.
|
|
|
+
|
|
|
+If @id{glb} is true,
|
|
|
+also stores the module into global @id{modname}.
|
|
|
+
|
|
|
+Leaves a copy of the module on the stack.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup);|
|
|
|
+@apii{nup,0,m}
|
|
|
+
|
|
|
+Registers all functions in the array @id{l}
|
|
|
+@seeC{luaL_Reg} into the table on the top of the stack
|
|
|
+(below optional upvalues, see next).
|
|
|
+
|
|
|
+When @id{nup} is not zero,
|
|
|
+all functions are created with @id{nup} upvalues,
|
|
|
+initialized with copies of the @id{nup} values
|
|
|
+previously pushed on the stack
|
|
|
+on top of the library table.
|
|
|
+These values are popped from the stack after the registration.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_setmetatable (lua_State *L, const char *tname);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Sets the metatable of the object at the top of the stack
|
|
|
+as the metatable associated with name @id{tname}
|
|
|
+in the registry @seeC{luaL_newmetatable}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+typedef struct luaL_Stream {
|
|
|
+ FILE *f;
|
|
|
+ lua_CFunction closef;
|
|
|
+} luaL_Stream;
|
|
|
+|
|
|
|
+
|
|
|
+The standard representation for @x{file handles},
|
|
|
+which is used by the standard I/O library.
|
|
|
+
|
|
|
+A file handle is implemented as a full userdata,
|
|
|
+with a metatable called @id{LUA_FILEHANDLE}
|
|
|
+(where @id{LUA_FILEHANDLE} is a macro with the actual metatable's name).
|
|
|
+The metatable is created by the I/O library
|
|
|
+@seeF{luaL_newmetatable}.
|
|
|
+
|
|
|
+This userdata must start with the structure @id{luaL_Stream};
|
|
|
+it can contain other data after this initial structure.
|
|
|
+Field @id{f} points to the corresponding C stream
|
|
|
+(or it can be @id{NULL} to indicate an incompletely created handle).
|
|
|
+Field @id{closef} points to a Lua function
|
|
|
+that will be called to close the stream
|
|
|
+when the handle is closed or collected;
|
|
|
+this function receives the file handle as its sole argument and
|
|
|
+must return either @true (in case of success)
|
|
|
+or @nil plus an error message (in case of error).
|
|
|
+Once Lua calls this field,
|
|
|
+it changes the field value to @id{NULL}
|
|
|
+to signal that the handle is closed.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void *luaL_testudata (lua_State *L, int arg, const char *tname);|
|
|
|
+@apii{0,0,m}
|
|
|
+
|
|
|
+This function works like @Lid{luaL_checkudata},
|
|
|
+except that, when the test fails,
|
|
|
+it returns @id{NULL} instead of raising an error.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *luaL_tolstring (lua_State *L, int idx, size_t *len);|
|
|
|
+@apii{0,1,e}
|
|
|
+
|
|
|
+Converts any Lua value at the given index to a @N{C string}
|
|
|
+in a reasonable format.
|
|
|
+The resulting string is pushed onto the stack and also
|
|
|
+returned by the function.
|
|
|
+If @id{len} is not @id{NULL},
|
|
|
+the function also sets @T{*len} with the string length.
|
|
|
+
|
|
|
+If the value has a metatable with a @idx{__tostring} field,
|
|
|
+then @id{luaL_tolstring} calls the corresponding metamethod
|
|
|
+with the value as argument,
|
|
|
+and uses the result of the call as its result.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{
|
|
|
+void luaL_traceback (lua_State *L, lua_State *L1, const char *msg,
|
|
|
+ int level);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Creates and pushes a traceback of the stack @id{L1}.
|
|
|
+If @id{msg} is not @id{NULL} it is appended
|
|
|
+at the beginning of the traceback.
|
|
|
+The @id{level} parameter tells at which level
|
|
|
+to start the traceback.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{const char *luaL_typename (lua_State *L, int index);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Returns the name of the type of the value at the given index.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_unref (lua_State *L, int t, int ref);|
|
|
|
+@apii{0,0,-}
|
|
|
+
|
|
|
+Releases reference @id{ref} from the table at index @id{t}
|
|
|
+@seeC{luaL_ref}.
|
|
|
+The entry is removed from the table,
|
|
|
+so that the referred object can be collected.
|
|
|
+The reference @id{ref} is also freed to be used again.
|
|
|
+
|
|
|
+If @id{ref} is @Lid{LUA_NOREF} or @Lid{LUA_REFNIL},
|
|
|
+@Lid{luaL_unref} does nothing.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@APIEntry{void luaL_where (lua_State *L, int lvl);|
|
|
|
+@apii{0,1,m}
|
|
|
+
|
|
|
+Pushes onto the stack a string identifying the current position
|
|
|
+of the control at level @id{lvl} in the call stack.
|
|
|
+Typically this string has the following format:
|
|
|
+@verbatim{
|
|
|
+@rep{chunkname}:@rep{currentline}:
|
|
|
+}
|
|
|
+@N{Level 0} is the running function,
|
|
|
+@N{level 1} is the function that called the running function,
|
|
|
+etc.
|
|
|
+
|
|
|
+This function is used to build a prefix for error messages.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@C{-------------------------------------------------------------------------}
|
|
|
+@sect1{libraries| @title{Standard Libraries}
|
|
|
+
|
|
|
+The standard Lua libraries provide useful functions
|
|
|
+that are implemented directly through the @N{C API}.
|
|
|
+Some of these functions provide essential services to the language
|
|
|
+(e.g., @Lid{type} and @Lid{getmetatable});
|
|
|
+others provide access to @Q{outside} services (e.g., I/O);
|
|
|
+and others could be implemented in Lua itself,
|
|
|
+but are quite useful or have critical performance requirements that
|
|
|
+deserve an implementation in C (e.g., @Lid{table.sort}).
|
|
|
+
|
|
|
+All libraries are implemented through the official @N{C API}
|
|
|
+and are provided as separate @N{C modules}.
|
|
|
+Unless otherwise noted,
|
|
|
+these library functions do not adjust its number of arguments
|
|
|
+to its expected parameters.
|
|
|
+For instance, a function documented as @T{foo(arg)}
|
|
|
+should not be called without an argument.
|
|
|
+
|
|
|
+Currently, Lua has the following standard libraries:
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{@link{predefined|basic library};}
|
|
|
+
|
|
|
+@item{@link{corolib|coroutine library};}
|
|
|
+
|
|
|
+@item{@link{packlib|package library};}
|
|
|
+
|
|
|
+@item{@link{strlib|string manipulation};}
|
|
|
+
|
|
|
+@item{@link{utf8|basic UTF-8 support};}
|
|
|
+
|
|
|
+@item{@link{tablib|table manipulation};}
|
|
|
+
|
|
|
+@item{@link{mathlib|mathematical functions} (sin, log, etc.);}
|
|
|
+
|
|
|
+@item{@link{iolib|input and output};}
|
|
|
+
|
|
|
+@item{@link{oslib|operating system facilities};}
|
|
|
+
|
|
|
+@item{@link{debuglib|debug facilities}.}
|
|
|
+
|
|
|
+}
|
|
|
+Except for the basic and the package libraries,
|
|
|
+each library provides all its functions as fields of a global table
|
|
|
+or as methods of its objects.
|
|
|
+
|
|
|
+To have access to these libraries,
|
|
|
+the @N{C host} program should call the @Lid{luaL_openlibs} function,
|
|
|
+which opens all standard libraries.
|
|
|
+Alternatively,
|
|
|
+the host program can open them individually by using
|
|
|
+@Lid{luaL_requiref} to call
|
|
|
+@defid{luaopen_base} (for the basic library),
|
|
|
+@defid{luaopen_package} (for the package library),
|
|
|
+@defid{luaopen_coroutine} (for the coroutine library),
|
|
|
+@defid{luaopen_string} (for the string library),
|
|
|
+@defid{luaopen_utf8} (for the UTF8 library),
|
|
|
+@defid{luaopen_table} (for the table library),
|
|
|
+@defid{luaopen_math} (for the mathematical library),
|
|
|
+@defid{luaopen_io} (for the I/O library),
|
|
|
+@defid{luaopen_os} (for the operating system library),
|
|
|
+and @defid{luaopen_debug} (for the debug library).
|
|
|
+These functions are declared in @defid{lualib.h}.
|
|
|
+
|
|
|
+@sect2{predefined| @title{Basic Functions}
|
|
|
+
|
|
|
+The basic library provides core functions to Lua.
|
|
|
+If you do not include this library in your application,
|
|
|
+you should check carefully whether you need to provide
|
|
|
+implementations for some of its facilities.
|
|
|
+
|
|
|
+
|
|
|
+@LibEntry{assert (v [, message])|
|
|
|
+
|
|
|
+Calls @Lid{error} if
|
|
|
+the value of its argument @id{v} is false (i.e., @nil or @false);
|
|
|
+otherwise, returns all its arguments.
|
|
|
+In case of error,
|
|
|
+@id{message} is the error object;
|
|
|
+when absent, it defaults to @St{assertion failed!}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{collectgarbage ([opt [, arg]])|
|
|
|
+
|
|
|
+This function is a generic interface to the garbage collector.
|
|
|
+It performs different functions according to its first argument, @id{opt}:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@St{collect}|
|
|
|
+performs a full garbage-collection cycle.
|
|
|
+This is the default option.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{stop}|
|
|
|
+stops automatic execution of the garbage collector.
|
|
|
+The collector will run only when explicitly invoked,
|
|
|
+until a call to restart it.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{restart}|
|
|
|
+restarts automatic execution of the garbage collector.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{count}|
|
|
|
+returns the total memory in use by Lua in Kbytes.
|
|
|
+The value has a fractional part,
|
|
|
+so that it multiplied by 1024
|
|
|
+gives the exact number of bytes in use by Lua
|
|
|
+(except for overflows).
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{step}|
|
|
|
+performs a garbage-collection step.
|
|
|
+The step @Q{size} is controlled by @id{arg}.
|
|
|
+With a zero value,
|
|
|
+the collector will perform one basic (indivisible) step.
|
|
|
+For non-zero values,
|
|
|
+the collector will perform as if that amount of memory
|
|
|
+(in KBytes) had been allocated by Lua.
|
|
|
+Returns @true if the step finished a collection cycle.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{setpause}|
|
|
|
+sets @id{arg} as the new value for the @emph{pause} of
|
|
|
+the collector @see{GC}.
|
|
|
+Returns the previous value for @emph{pause}.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{incremental}|
|
|
|
+Change the collector mode to incremental.
|
|
|
+This option can be followed by three numbers:
|
|
|
+the garbage-collector pause,
|
|
|
+the step multiplier,
|
|
|
+and the step size.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{generational}|
|
|
|
+Change the collector mode to generational.
|
|
|
+This option can be followed by two numbers:
|
|
|
+the garbage-collector minor multiplier
|
|
|
+and the major multiplier.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{isrunning}|
|
|
|
+returns a boolean that tells whether the collector is running
|
|
|
+(i.e., not stopped).
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{dofile ([filename])|
|
|
|
+Opens the named file and executes its contents as a Lua chunk.
|
|
|
+When called without arguments,
|
|
|
+@id{dofile} executes the contents of the standard input (@id{stdin}).
|
|
|
+Returns all values returned by the chunk.
|
|
|
+In case of errors, @id{dofile} propagates the error
|
|
|
+to its caller (that is, @id{dofile} does not run in protected mode).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{error (message [, level])|
|
|
|
+Terminates the last protected function called
|
|
|
+and returns @id{message} as the error object.
|
|
|
+Function @id{error} never returns.
|
|
|
+
|
|
|
+Usually, @id{error} adds some information about the error position
|
|
|
+at the beginning of the message, if the message is a string.
|
|
|
+The @id{level} argument specifies how to get the error position.
|
|
|
+With @N{level 1} (the default), the error position is where the
|
|
|
+@id{error} function was called.
|
|
|
+@N{Level 2} points the error to where the function
|
|
|
+that called @id{error} was called; and so on.
|
|
|
+Passing a @N{level 0} avoids the addition of error position information
|
|
|
+to the message.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{_G|
|
|
|
+A global variable (not a function) that
|
|
|
+holds the @x{global environment} @see{globalenv}.
|
|
|
+Lua itself does not use this variable;
|
|
|
+changing its value does not affect any environment,
|
|
|
+nor vice versa.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{getmetatable (object)|
|
|
|
+
|
|
|
+If @id{object} does not have a metatable, returns @nil.
|
|
|
+Otherwise,
|
|
|
+if the object's metatable has a @idx{__metatable} field,
|
|
|
+returns the associated value.
|
|
|
+Otherwise, returns the metatable of the given object.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{ipairs (t)|
|
|
|
+
|
|
|
+Returns three values (an iterator function, the table @id{t}, and 0)
|
|
|
+so that the construction
|
|
|
+@verbatim{
|
|
|
+for i,v in ipairs(t) do @rep{body} end
|
|
|
+}
|
|
|
+will iterate over the key@En{}value pairs
|
|
|
+(@T{1,t[1]}), (@T{2,t[2]}), @ldots,
|
|
|
+up to the first absent index.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{load (chunk [, chunkname [, mode [, env]]])|
|
|
|
+
|
|
|
+Loads a chunk.
|
|
|
+
|
|
|
+If @id{chunk} is a string, the chunk is this string.
|
|
|
+If @id{chunk} is a function,
|
|
|
+@id{load} calls it repeatedly to get the chunk pieces.
|
|
|
+Each call to @id{chunk} must return a string that concatenates
|
|
|
+with previous results.
|
|
|
+A return of an empty string, @nil, or no value signals the end of the chunk.
|
|
|
+
|
|
|
+If there are no syntactic errors,
|
|
|
+returns the compiled chunk as a function;
|
|
|
+otherwise, returns @nil plus the error message.
|
|
|
+
|
|
|
+If the resulting function has upvalues,
|
|
|
+the first upvalue is set to the value of @id{env},
|
|
|
+if that parameter is given,
|
|
|
+or to the value of the @x{global environment}.
|
|
|
+Other upvalues are initialized with @nil.
|
|
|
+(When you load a main chunk,
|
|
|
+the resulting function will always have exactly one upvalue,
|
|
|
+the @id{_ENV} variable @see{globalenv}.
|
|
|
+However,
|
|
|
+when you load a binary chunk created from a function @seeF{string.dump},
|
|
|
+the resulting function can have an arbitrary number of upvalues.)
|
|
|
+All upvalues are fresh, that is,
|
|
|
+they are not shared with any other function.
|
|
|
+
|
|
|
+@id{chunkname} is used as the name of the chunk for error messages
|
|
|
+and debug information @see{debugI}.
|
|
|
+When absent,
|
|
|
+it defaults to @id{chunk}, if @id{chunk} is a string,
|
|
|
+or to @St{=(load)} otherwise.
|
|
|
+
|
|
|
+The string @id{mode} controls whether the chunk can be text or binary
|
|
|
+(that is, a precompiled chunk).
|
|
|
+It may be the string @St{b} (only @x{binary chunk}s),
|
|
|
+@St{t} (only text chunks),
|
|
|
+or @St{bt} (both binary and text).
|
|
|
+The default is @St{bt}.
|
|
|
+
|
|
|
+Lua does not check the consistency of binary chunks.
|
|
|
+Maliciously crafted binary chunks can crash
|
|
|
+the interpreter.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{loadfile ([filename [, mode [, env]]])|
|
|
|
+
|
|
|
+Similar to @Lid{load},
|
|
|
+but gets the chunk from file @id{filename}
|
|
|
+or from the standard input,
|
|
|
+if no file name is given.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{next (table [, index])|
|
|
|
+
|
|
|
+Allows a program to traverse all fields of a table.
|
|
|
+Its first argument is a table and its second argument
|
|
|
+is an index in this table.
|
|
|
+@id{next} returns the next index of the table
|
|
|
+and its associated value.
|
|
|
+When called with @nil as its second argument,
|
|
|
+@id{next} returns an initial index
|
|
|
+and its associated value.
|
|
|
+When called with the last index,
|
|
|
+or with @nil in an empty table,
|
|
|
+@id{next} returns @nil.
|
|
|
+If the second argument is absent, then it is interpreted as @nil.
|
|
|
+In particular,
|
|
|
+you can use @T{next(t)} to check whether a table is empty.
|
|
|
+
|
|
|
+The order in which the indices are enumerated is not specified,
|
|
|
+@emph{even for numeric indices}.
|
|
|
+(To traverse a table in numerical order,
|
|
|
+use a numerical @Rw{for}.)
|
|
|
+
|
|
|
+The behavior of @id{next} is undefined if,
|
|
|
+during the traversal,
|
|
|
+you assign any value to a non-existent field in the table.
|
|
|
+You may however modify existing fields.
|
|
|
+In particular, you may set existing fields to nil.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{pairs (t)|
|
|
|
+
|
|
|
+If @id{t} has a metamethod @idx{__pairs},
|
|
|
+calls it with @id{t} as argument and returns the first three
|
|
|
+results from the call.
|
|
|
+
|
|
|
+Otherwise,
|
|
|
+returns three values: the @Lid{next} function, the table @id{t}, and @nil,
|
|
|
+so that the construction
|
|
|
+@verbatim{
|
|
|
+for k,v in pairs(t) do @rep{body} end
|
|
|
+}
|
|
|
+will iterate over all key@En{}value pairs of table @id{t}.
|
|
|
+
|
|
|
+See function @Lid{next} for the caveats of modifying
|
|
|
+the table during its traversal.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{pcall (f [, arg1, @Cdots])|
|
|
|
+
|
|
|
+Calls function @id{f} with
|
|
|
+the given arguments in @def{protected mode}.
|
|
|
+This means that any error @N{inside @T{f}} is not propagated;
|
|
|
+instead, @id{pcall} catches the error
|
|
|
+and returns a status code.
|
|
|
+Its first result is the status code (a boolean),
|
|
|
+which is true if the call succeeds without errors.
|
|
|
+In such case, @id{pcall} also returns all results from the call,
|
|
|
+after this first result.
|
|
|
+In case of any error, @id{pcall} returns @false plus the error message.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{print (@Cdots)|
|
|
|
+Receives any number of arguments
|
|
|
+and prints their values to @id{stdout},
|
|
|
+using the @Lid{tostring} function to convert each argument to a string.
|
|
|
+@id{print} is not intended for formatted output,
|
|
|
+but only as a quick way to show a value,
|
|
|
+for instance for debugging.
|
|
|
+For complete control over the output,
|
|
|
+use @Lid{string.format} and @Lid{io.write}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{rawequal (v1, v2)|
|
|
|
+Checks whether @id{v1} is equal to @id{v2},
|
|
|
+without invoking the @idx{__eq} metamethod.
|
|
|
+Returns a boolean.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{rawget (table, index)|
|
|
|
+Gets the real value of @T{table[index]},
|
|
|
+without invoking the @idx{__index} metamethod.
|
|
|
+@id{table} must be a table;
|
|
|
+@id{index} may be any value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{rawlen (v)|
|
|
|
+Returns the length of the object @id{v},
|
|
|
+which must be a table or a string,
|
|
|
+without invoking the @idx{__len} metamethod.
|
|
|
+Returns an integer.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{rawset (table, index, value)|
|
|
|
+Sets the real value of @T{table[index]} to @id{value},
|
|
|
+without invoking the @idx{__newindex} metamethod.
|
|
|
+@id{table} must be a table,
|
|
|
+@id{index} any value different from @nil and @x{NaN},
|
|
|
+and @id{value} any Lua value.
|
|
|
+
|
|
|
+This function returns @id{table}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{select (index, @Cdots)|
|
|
|
+
|
|
|
+If @id{index} is a number,
|
|
|
+returns all arguments after argument number @id{index};
|
|
|
+a negative number indexes from the end (@num{-1} is the last argument).
|
|
|
+Otherwise, @id{index} must be the string @T{"#"},
|
|
|
+and @id{select} returns the total number of extra arguments it received.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{setmetatable (table, metatable)|
|
|
|
+
|
|
|
+Sets the metatable for the given table.
|
|
|
+(To change the metatable of other types from Lua code,
|
|
|
+you must use the @link{debuglib|debug library}.)
|
|
|
+If @id{metatable} is @nil,
|
|
|
+removes the metatable of the given table.
|
|
|
+If the original metatable has a @idx{__metatable} field,
|
|
|
+raises an error.
|
|
|
+
|
|
|
+This function returns @id{table}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{tonumber (e [, base])|
|
|
|
+
|
|
|
+When called with no @id{base},
|
|
|
+@id{tonumber} tries to convert its argument to a number.
|
|
|
+If the argument is already a number or
|
|
|
+a string convertible to a number,
|
|
|
+then @id{tonumber} returns this number;
|
|
|
+otherwise, it returns @nil.
|
|
|
+
|
|
|
+The conversion of strings can result in integers or floats,
|
|
|
+according to the lexical conventions of Lua @see{lexical}.
|
|
|
+(The string may have leading and trailing spaces and a sign.)
|
|
|
+
|
|
|
+When called with @id{base},
|
|
|
+then @id{e} must be a string to be interpreted as
|
|
|
+an integer numeral in that base.
|
|
|
+The base may be any integer between 2 and 36, inclusive.
|
|
|
+In bases @N{above 10}, the letter @Char{A} (in either upper or lower case)
|
|
|
+@N{represents 10}, @Char{B} @N{represents 11}, and so forth,
|
|
|
+with @Char{Z} representing 35.
|
|
|
+If the string @id{e} is not a valid numeral in the given base,
|
|
|
+the function returns @nil.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{tostring (v)|
|
|
|
+Receives a value of any type and
|
|
|
+converts it to a string in a human-readable format.
|
|
|
+(For complete control of how numbers are converted,
|
|
|
+use @Lid{string.format}.)
|
|
|
+
|
|
|
+If the metatable of @id{v} has a @idx{__tostring} field,
|
|
|
+then @id{tostring} calls the corresponding value
|
|
|
+with @id{v} as argument,
|
|
|
+and uses the result of the call as its result.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{type (v)|
|
|
|
+Returns the type of its only argument, coded as a string.
|
|
|
+The possible results of this function are
|
|
|
+@St{nil} (a string, not the value @nil),
|
|
|
+@St{number},
|
|
|
+@St{string},
|
|
|
+@St{boolean},
|
|
|
+@St{table},
|
|
|
+@St{function},
|
|
|
+@St{thread},
|
|
|
+and @St{userdata}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{_VERSION|
|
|
|
+
|
|
|
+A global variable (not a function) that
|
|
|
+holds a string containing the running Lua version.
|
|
|
+The current value of this variable is @St{Lua 5.4}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{xpcall (f, msgh [, arg1, @Cdots])|
|
|
|
+
|
|
|
+This function is similar to @Lid{pcall},
|
|
|
+except that it sets a new @x{message handler} @id{msgh}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{corolib| @title{Coroutine Manipulation}
|
|
|
+
|
|
|
+This library comprises the operations to manipulate coroutines,
|
|
|
+which come inside the table @defid{coroutine}.
|
|
|
+See @See{coroutine} for a general description of coroutines.
|
|
|
+
|
|
|
+
|
|
|
+@LibEntry{coroutine.create (f)|
|
|
|
+
|
|
|
+Creates a new coroutine, with body @id{f}.
|
|
|
+@id{f} must be a function.
|
|
|
+Returns this new coroutine,
|
|
|
+an object with type @T{"thread"}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{coroutine.isyieldable ()|
|
|
|
+
|
|
|
+Returns true when the running coroutine can yield.
|
|
|
+
|
|
|
+A running coroutine is yieldable if it is not the main thread and
|
|
|
+it is not inside a non-yieldable @N{C function}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{coroutine.resume (co [, val1, @Cdots])|
|
|
|
+
|
|
|
+Starts or continues the execution of coroutine @id{co}.
|
|
|
+The first time you resume a coroutine,
|
|
|
+it starts running its body.
|
|
|
+The values @id{val1}, @ldots are passed
|
|
|
+as the arguments to the body function.
|
|
|
+If the coroutine has yielded,
|
|
|
+@id{resume} restarts it;
|
|
|
+the values @id{val1}, @ldots are passed
|
|
|
+as the results from the yield.
|
|
|
+
|
|
|
+If the coroutine runs without any errors,
|
|
|
+@id{resume} returns @true plus any values passed to @id{yield}
|
|
|
+(when the coroutine yields) or any values returned by the body function
|
|
|
+(when the coroutine terminates).
|
|
|
+If there is any error,
|
|
|
+@id{resume} returns @false plus the error message.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{coroutine.running ()|
|
|
|
+
|
|
|
+Returns the running coroutine plus a boolean,
|
|
|
+true when the running coroutine is the main one.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{coroutine.status (co)|
|
|
|
+
|
|
|
+Returns the status of coroutine @id{co}, as a string:
|
|
|
+@T{"running"},
|
|
|
+if the coroutine is running (that is, it called @id{status});
|
|
|
+@T{"suspended"}, if the coroutine is suspended in a call to @id{yield},
|
|
|
+or if it has not started running yet;
|
|
|
+@T{"normal"} if the coroutine is active but not running
|
|
|
+(that is, it has resumed another coroutine);
|
|
|
+and @T{"dead"} if the coroutine has finished its body function,
|
|
|
+or if it has stopped with an error.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{coroutine.wrap (f)|
|
|
|
+
|
|
|
+Creates a new coroutine, with body @id{f}.
|
|
|
+@id{f} must be a function.
|
|
|
+Returns a function that resumes the coroutine each time it is called.
|
|
|
+Any arguments passed to the function behave as the
|
|
|
+extra arguments to @id{resume}.
|
|
|
+Returns the same values returned by @id{resume},
|
|
|
+except the first boolean.
|
|
|
+In case of error, propagates the error.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{coroutine.yield (@Cdots)|
|
|
|
+
|
|
|
+Suspends the execution of the calling coroutine.
|
|
|
+Any arguments to @id{yield} are passed as extra results to @id{resume}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{packlib| @title{Modules}
|
|
|
+
|
|
|
+The package library provides basic
|
|
|
+facilities for loading modules in Lua.
|
|
|
+It exports one function directly in the global environment:
|
|
|
+@Lid{require}.
|
|
|
+Everything else is exported in a table @defid{package}.
|
|
|
+
|
|
|
+
|
|
|
+@LibEntry{require (modname)|
|
|
|
+
|
|
|
+Loads the given module.
|
|
|
+The function starts by looking into the @Lid{package.loaded} table
|
|
|
+to determine whether @id{modname} is already loaded.
|
|
|
+If it is, then @id{require} returns the value stored
|
|
|
+at @T{package.loaded[modname]}.
|
|
|
+Otherwise, it tries to find a @emph{loader} for the module.
|
|
|
+
|
|
|
+To find a loader,
|
|
|
+@id{require} is guided by the @Lid{package.searchers} sequence.
|
|
|
+By changing this sequence,
|
|
|
+we can change how @id{require} looks for a module.
|
|
|
+The following explanation is based on the default configuration
|
|
|
+for @Lid{package.searchers}.
|
|
|
+
|
|
|
+First @id{require} queries @T{package.preload[modname]}.
|
|
|
+If it has a value,
|
|
|
+this value (which must be a function) is the loader.
|
|
|
+Otherwise @id{require} searches for a Lua loader using the
|
|
|
+path stored in @Lid{package.path}.
|
|
|
+If that also fails, it searches for a @N{C loader} using the
|
|
|
+path stored in @Lid{package.cpath}.
|
|
|
+If that also fails,
|
|
|
+it tries an @emph{all-in-one} loader @seeF{package.searchers}.
|
|
|
+
|
|
|
+Once a loader is found,
|
|
|
+@id{require} calls the loader with two arguments:
|
|
|
+@id{modname} and an extra value dependent on how it got the loader.
|
|
|
+(If the loader came from a file,
|
|
|
+this extra value is the file name.)
|
|
|
+If the loader returns any non-nil value,
|
|
|
+@id{require} assigns the returned value to @T{package.loaded[modname]}.
|
|
|
+If the loader does not return a non-nil value and
|
|
|
+has not assigned any value to @T{package.loaded[modname]},
|
|
|
+then @id{require} assigns @Rw{true} to this entry.
|
|
|
+In any case, @id{require} returns the
|
|
|
+final value of @T{package.loaded[modname]}.
|
|
|
+
|
|
|
+If there is any error loading or running the module,
|
|
|
+or if it cannot find any loader for the module,
|
|
|
+then @id{require} raises an error.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{package.config|
|
|
|
+
|
|
|
+A string describing some compile-time configurations for packages.
|
|
|
+This string is a sequence of lines:
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{The first line is the @x{directory separator} string.
|
|
|
+Default is @Char{\} for @x{Windows} and @Char{/} for all other systems.}
|
|
|
+
|
|
|
+@item{The second line is the character that separates templates in a path.
|
|
|
+Default is @Char{;}.}
|
|
|
+
|
|
|
+@item{The third line is the string that marks the
|
|
|
+substitution points in a template.
|
|
|
+Default is @Char{?}.}
|
|
|
+
|
|
|
+@item{The fourth line is a string that, in a path in @x{Windows},
|
|
|
+is replaced by the executable's directory.
|
|
|
+Default is @Char{!}.}
|
|
|
+
|
|
|
+@item{The fifth line is a mark to ignore all text after it
|
|
|
+when building the @id{luaopen_} function name.
|
|
|
+Default is @Char{-}.}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{package.cpath|
|
|
|
+
|
|
|
+The path used by @Lid{require} to search for a @N{C loader}.
|
|
|
+
|
|
|
+Lua initializes the @N{C path} @Lid{package.cpath} in the same way
|
|
|
+it initializes the Lua path @Lid{package.path},
|
|
|
+using the environment variable @defid{LUA_CPATH_5_4},
|
|
|
+or the environment variable @defid{LUA_CPATH},
|
|
|
+or a default path defined in @id{luaconf.h}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{package.loaded|
|
|
|
+
|
|
|
+A table used by @Lid{require} to control which
|
|
|
+modules are already loaded.
|
|
|
+When you require a module @id{modname} and
|
|
|
+@T{package.loaded[modname]} is not false,
|
|
|
+@Lid{require} simply returns the value stored there.
|
|
|
+
|
|
|
+This variable is only a reference to the real table;
|
|
|
+assignments to this variable do not change the
|
|
|
+table used by @Lid{require}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{package.loadlib (libname, funcname)|
|
|
|
+
|
|
|
+Dynamically links the host program with the @N{C library} @id{libname}.
|
|
|
+
|
|
|
+If @id{funcname} is @St{*},
|
|
|
+then it only links with the library,
|
|
|
+making the symbols exported by the library
|
|
|
+available to other dynamically linked libraries.
|
|
|
+Otherwise,
|
|
|
+it looks for a function @id{funcname} inside the library
|
|
|
+and returns this function as a @N{C function}.
|
|
|
+So, @id{funcname} must follow the @Lid{lua_CFunction} prototype
|
|
|
+@seeC{lua_CFunction}.
|
|
|
+
|
|
|
+This is a low-level function.
|
|
|
+It completely bypasses the package and module system.
|
|
|
+Unlike @Lid{require},
|
|
|
+it does not perform any path searching and
|
|
|
+does not automatically adds extensions.
|
|
|
+@id{libname} must be the complete file name of the @N{C library},
|
|
|
+including if necessary a path and an extension.
|
|
|
+@id{funcname} must be the exact name exported by the @N{C library}
|
|
|
+(which may depend on the @N{C compiler} and linker used).
|
|
|
+
|
|
|
+This function is not supported by @N{Standard C}.
|
|
|
+As such, it is only available on some platforms
|
|
|
+(Windows, Linux, Mac OS X, Solaris, BSD,
|
|
|
+plus other Unix systems that support the @id{dlfcn} standard).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{package.path|
|
|
|
+
|
|
|
+The path used by @Lid{require} to search for a Lua loader.
|
|
|
+
|
|
|
+At start-up, Lua initializes this variable with
|
|
|
+the value of the environment variable @defid{LUA_PATH_5_4} or
|
|
|
+the environment variable @defid{LUA_PATH} or
|
|
|
+with a default path defined in @id{luaconf.h},
|
|
|
+if those environment variables are not defined.
|
|
|
+Any @St{;;} in the value of the environment variable
|
|
|
+is replaced by the default path.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{package.preload|
|
|
|
+
|
|
|
+A table to store loaders for specific modules
|
|
|
+@seeF{require}.
|
|
|
+
|
|
|
+This variable is only a reference to the real table;
|
|
|
+assignments to this variable do not change the
|
|
|
+table used by @Lid{require}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{package.searchers|
|
|
|
+
|
|
|
+A table used by @Lid{require} to control how to load modules.
|
|
|
+
|
|
|
+Each entry in this table is a @def{searcher function}.
|
|
|
+When looking for a module,
|
|
|
+@Lid{require} calls each of these searchers in ascending order,
|
|
|
+with the module name (the argument given to @Lid{require}) as its
|
|
|
+sole parameter.
|
|
|
+The function can return another function (the module @def{loader})
|
|
|
+plus an extra value that will be passed to that loader,
|
|
|
+or a string explaining why it did not find that module
|
|
|
+(or @nil if it has nothing to say).
|
|
|
+
|
|
|
+Lua initializes this table with four searcher functions.
|
|
|
+
|
|
|
+The first searcher simply looks for a loader in the
|
|
|
+@Lid{package.preload} table.
|
|
|
+
|
|
|
+The second searcher looks for a loader as a Lua library,
|
|
|
+using the path stored at @Lid{package.path}.
|
|
|
+The search is done as described in function @Lid{package.searchpath}.
|
|
|
+
|
|
|
+The third searcher looks for a loader as a @N{C library},
|
|
|
+using the path given by the variable @Lid{package.cpath}.
|
|
|
+Again,
|
|
|
+the search is done as described in function @Lid{package.searchpath}.
|
|
|
+For instance,
|
|
|
+if the @N{C path} is the string
|
|
|
+@verbatim{
|
|
|
+"./?.so;./?.dll;/usr/local/?/init.so"
|
|
|
+}
|
|
|
+the searcher for module @id{foo}
|
|
|
+will try to open the files @T{./foo.so}, @T{./foo.dll},
|
|
|
+and @T{/usr/local/foo/init.so}, in that order.
|
|
|
+Once it finds a @N{C library},
|
|
|
+this searcher first uses a dynamic link facility to link the
|
|
|
+application with the library.
|
|
|
+Then it tries to find a @N{C function} inside the library to
|
|
|
+be used as the loader.
|
|
|
+The name of this @N{C function} is the string @St{luaopen_}
|
|
|
+concatenated with a copy of the module name where each dot
|
|
|
+is replaced by an underscore.
|
|
|
+Moreover, if the module name has a hyphen,
|
|
|
+its suffix after (and including) the first hyphen is removed.
|
|
|
+For instance, if the module name is @id{a.b.c-v2.1},
|
|
|
+the function name will be @id{luaopen_a_b_c}.
|
|
|
+
|
|
|
+The fourth searcher tries an @def{all-in-one loader}.
|
|
|
+It searches the @N{C path} for a library for
|
|
|
+the root name of the given module.
|
|
|
+For instance, when requiring @id{a.b.c},
|
|
|
+it will search for a @N{C library} for @id{a}.
|
|
|
+If found, it looks into it for an open function for
|
|
|
+the submodule;
|
|
|
+in our example, that would be @id{luaopen_a_b_c}.
|
|
|
+With this facility, a package can pack several @N{C submodules}
|
|
|
+into one single library,
|
|
|
+with each submodule keeping its original open function.
|
|
|
+
|
|
|
+All searchers except the first one (preload) return as the extra value
|
|
|
+the file name where the module was found,
|
|
|
+as returned by @Lid{package.searchpath}.
|
|
|
+The first searcher returns no extra value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{package.searchpath (name, path [, sep [, rep]])|
|
|
|
+
|
|
|
+Searches for the given @id{name} in the given @id{path}.
|
|
|
+
|
|
|
+A path is a string containing a sequence of
|
|
|
+@emph{templates} separated by semicolons.
|
|
|
+For each template,
|
|
|
+the function replaces each interrogation mark (if any)
|
|
|
+in the template with a copy of @id{name}
|
|
|
+wherein all occurrences of @id{sep}
|
|
|
+(a dot, by default)
|
|
|
+were replaced by @id{rep}
|
|
|
+(the system's directory separator, by default),
|
|
|
+and then tries to open the resulting file name.
|
|
|
+
|
|
|
+For instance, if the path is the string
|
|
|
+@verbatim{
|
|
|
+"./?.lua;./?.lc;/usr/local/?/init.lua"
|
|
|
+}
|
|
|
+the search for the name @id{foo.a}
|
|
|
+will try to open the files
|
|
|
+@T{./foo/a.lua}, @T{./foo/a.lc}, and
|
|
|
+@T{/usr/local/foo/a/init.lua}, in that order.
|
|
|
+
|
|
|
+Returns the resulting name of the first file that it can
|
|
|
+open in read mode (after closing the file),
|
|
|
+or @nil plus an error message if none succeeds.
|
|
|
+(This error message lists all file names it tried to open.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{strlib| @title{String Manipulation}
|
|
|
+
|
|
|
+This library provides generic functions for string manipulation,
|
|
|
+such as finding and extracting substrings, and pattern matching.
|
|
|
+When indexing a string in Lua, the first character is at @N{position 1}
|
|
|
+(not @N{at 0}, as in C).
|
|
|
+Indices are allowed to be negative and are interpreted as indexing backwards,
|
|
|
+from the end of the string.
|
|
|
+Thus, the last character is at position @num{-1}, and so on.
|
|
|
+
|
|
|
+The string library provides all its functions inside the table
|
|
|
+@defid{string}.
|
|
|
+It also sets a @x{metatable for strings}
|
|
|
+where the @idx{__index} field points to the @id{string} table.
|
|
|
+Therefore, you can use the string functions in object-oriented style.
|
|
|
+For instance, @T{string.byte(s,i)}
|
|
|
+can be written as @T{s:byte(i)}.
|
|
|
+
|
|
|
+The string library assumes one-byte character encodings.
|
|
|
+
|
|
|
+
|
|
|
+@LibEntry{string.byte (s [, i [, j]])|
|
|
|
+Returns the internal numeric codes of the characters @T{s[i]},
|
|
|
+@T{s[i+1]}, @ldots, @T{s[j]}.
|
|
|
+The default value for @id{i} @N{is 1};
|
|
|
+the default value for @id{j} @N{is @id{i}}.
|
|
|
+These indices are corrected
|
|
|
+following the same rules of function @Lid{string.sub}.
|
|
|
+
|
|
|
+Numeric codes are not necessarily portable across platforms.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.char (@Cdots)|
|
|
|
+Receives zero or more integers.
|
|
|
+Returns a string with length equal to the number of arguments,
|
|
|
+in which each character has the internal numeric code equal
|
|
|
+to its corresponding argument.
|
|
|
+
|
|
|
+Numeric codes are not necessarily portable across platforms.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.dump (function [, strip])|
|
|
|
+
|
|
|
+Returns a string containing a binary representation
|
|
|
+(a @emph{binary chunk})
|
|
|
+of the given function,
|
|
|
+so that a later @Lid{load} on this string returns
|
|
|
+a copy of the function (but with new upvalues).
|
|
|
+If @id{strip} is a true value,
|
|
|
+the binary representation may not include all debug information
|
|
|
+about the function,
|
|
|
+to save space.
|
|
|
+
|
|
|
+Functions with upvalues have only their number of upvalues saved.
|
|
|
+When (re)loaded,
|
|
|
+those upvalues receive fresh instances containing @nil.
|
|
|
+(You can use the debug library to serialize
|
|
|
+and reload the upvalues of a function
|
|
|
+in a way adequate to your needs.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.find (s, pattern [, init [, plain]])|
|
|
|
+
|
|
|
+Looks for the first match of
|
|
|
+@id{pattern} @see{pm} in the string @id{s}.
|
|
|
+If it finds a match, then @id{find} returns the indices @N{of @T{s}}
|
|
|
+where this occurrence starts and ends;
|
|
|
+otherwise, it returns @nil.
|
|
|
+A third, optional numeric argument @id{init} specifies
|
|
|
+where to start the search;
|
|
|
+its default value @N{is 1} and can be negative.
|
|
|
+A value of @true as a fourth, optional argument @id{plain}
|
|
|
+turns off the pattern matching facilities,
|
|
|
+so the function does a plain @Q{find substring} operation,
|
|
|
+with no characters in @id{pattern} being considered magic.
|
|
|
+Note that if @id{plain} is given, then @id{init} must be given as well.
|
|
|
+
|
|
|
+If the pattern has captures,
|
|
|
+then in a successful match
|
|
|
+the captured values are also returned,
|
|
|
+after the two indices.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.format (formatstring, @Cdots)|
|
|
|
+
|
|
|
+Returns a formatted version of its variable number of arguments
|
|
|
+following the description given in its first argument (which must be a string).
|
|
|
+The format string follows the same rules as the @ANSI{sprintf}.
|
|
|
+The only differences are that the options/modifiers
|
|
|
+@T{*}, @id{h}, @id{L}, @id{l}, @id{n},
|
|
|
+and @id{p} are not supported
|
|
|
+and that there is an extra option, @id{q}.
|
|
|
+
|
|
|
+The @id{q} option formats booleans, nil, numbers, and strings
|
|
|
+in a way that the result is a valid constant in Lua source code.
|
|
|
+Booleans and nil are written in the obvious way
|
|
|
+(@id{true}, @id{false}, @id{nil}).
|
|
|
+Floats are written in hexadecimal,
|
|
|
+to preserve full precision.
|
|
|
+A string is written between double quotes,
|
|
|
+using escape sequences when necessary to ensure that
|
|
|
+it can safely be read back by the Lua interpreter.
|
|
|
+For instance, the call
|
|
|
+@verbatim{
|
|
|
+string.format('%q', 'a string with "quotes" and \n new line')
|
|
|
+}
|
|
|
+may produce the string:
|
|
|
+@verbatim{
|
|
|
+"a string with \"quotes\" and \
|
|
|
+ new line"
|
|
|
+}
|
|
|
+
|
|
|
+Options
|
|
|
+@id{A}, @id{a}, @id{E}, @id{e}, @id{f},
|
|
|
+@id{G}, and @id{g} all expect a number as argument.
|
|
|
+Options @id{c}, @id{d},
|
|
|
+@id{i}, @id{o}, @id{u}, @id{X}, and @id{x}
|
|
|
+expect an integer.
|
|
|
+When Lua is compiled with a C89 compiler,
|
|
|
+options @id{A} and @id{a} (hexadecimal floats)
|
|
|
+do not support any modifier (flags, width, length).
|
|
|
+
|
|
|
+Option @id{s} expects a string;
|
|
|
+if its argument is not a string,
|
|
|
+it is converted to one following the same rules of @Lid{tostring}.
|
|
|
+If the option has any modifier (flags, width, length),
|
|
|
+the string argument should not contain @x{embedded zeros}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.gmatch (s, pattern)|
|
|
|
+Returns an iterator function that,
|
|
|
+each time it is called,
|
|
|
+returns the next captures from @id{pattern} @see{pm}
|
|
|
+over the string @id{s}.
|
|
|
+If @id{pattern} specifies no captures,
|
|
|
+then the whole match is produced in each call.
|
|
|
+
|
|
|
+As an example, the following loop
|
|
|
+will iterate over all the words from string @id{s},
|
|
|
+printing one per line:
|
|
|
+@verbatim{
|
|
|
+s = "hello world from Lua"
|
|
|
+for w in string.gmatch(s, "%a+") do
|
|
|
+ print(w)
|
|
|
+end
|
|
|
+}
|
|
|
+The next example collects all pairs @T{key=value} from the
|
|
|
+given string into a table:
|
|
|
+@verbatim{
|
|
|
+t = {}
|
|
|
+s = "from=world, to=Lua"
|
|
|
+for k, v in string.gmatch(s, "(%w+)=(%w+)") do
|
|
|
+ t[k] = v
|
|
|
+end
|
|
|
+}
|
|
|
+
|
|
|
+For this function, a caret @Char{^} at the start of a pattern does not
|
|
|
+work as an anchor, as this would prevent the iteration.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.gsub (s, pattern, repl [, n])|
|
|
|
+Returns a copy of @id{s}
|
|
|
+in which all (or the first @id{n}, if given)
|
|
|
+occurrences of the @id{pattern} @see{pm} have been
|
|
|
+replaced by a replacement string specified by @id{repl},
|
|
|
+which can be a string, a table, or a function.
|
|
|
+@id{gsub} also returns, as its second value,
|
|
|
+the total number of matches that occurred.
|
|
|
+The name @id{gsub} comes from @emph{Global SUBstitution}.
|
|
|
+
|
|
|
+If @id{repl} is a string, then its value is used for replacement.
|
|
|
+The @N{character @T{%}} works as an escape character:
|
|
|
+any sequence in @id{repl} of the form @T{%@rep{d}},
|
|
|
+with @rep{d} between 1 and 9,
|
|
|
+stands for the value of the @rep{d}-th captured substring.
|
|
|
+The sequence @T{%0} stands for the whole match.
|
|
|
+The sequence @T{%%} stands for a @N{single @T{%}}.
|
|
|
+
|
|
|
+If @id{repl} is a table, then the table is queried for every match,
|
|
|
+using the first capture as the key.
|
|
|
+
|
|
|
+If @id{repl} is a function, then this function is called every time a
|
|
|
+match occurs, with all captured substrings passed as arguments,
|
|
|
+in order.
|
|
|
+
|
|
|
+In any case,
|
|
|
+if the pattern specifies no captures,
|
|
|
+then it behaves as if the whole pattern was inside a capture.
|
|
|
+
|
|
|
+If the value returned by the table query or by the function call
|
|
|
+is a string or a number,
|
|
|
+then it is used as the replacement string;
|
|
|
+otherwise, if it is @Rw{false} or @nil,
|
|
|
+then there is no replacement
|
|
|
+(that is, the original match is kept in the string).
|
|
|
+
|
|
|
+Here are some examples:
|
|
|
+@verbatim{
|
|
|
+x = string.gsub("hello world", "(%w+)", "%1 %1")
|
|
|
+--> x="hello hello world world"
|
|
|
+
|
|
|
+x = string.gsub("hello world", "%w+", "%0 %0", 1)
|
|
|
+--> x="hello hello world"
|
|
|
+
|
|
|
+x = string.gsub("hello world from Lua", "(%w+)%s*(%w+)", "%2 %1")
|
|
|
+--> x="world hello Lua from"
|
|
|
+
|
|
|
+x = string.gsub("home = $HOME, user = $USER", "%$(%w+)", os.getenv)
|
|
|
+--> x="home = /home/roberto, user = roberto"
|
|
|
+
|
|
|
+x = string.gsub("4+5 = $return 4+5$", "%$(.-)%$", function (s)
|
|
|
+ return load(s)()
|
|
|
+ end)
|
|
|
+--> x="4+5 = 9"
|
|
|
+
|
|
|
+local t = {name="lua", version="5.4"}
|
|
|
+x = string.gsub("$name-$version.tar.gz", "%$(%w+)", t)
|
|
|
+--> x="lua-5.4.tar.gz"
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.len (s)|
|
|
|
+Receives a string and returns its length.
|
|
|
+The empty string @T{""} has length 0.
|
|
|
+Embedded zeros are counted,
|
|
|
+so @T{"a\000bc\000"} has length 5.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.lower (s)|
|
|
|
+Receives a string and returns a copy of this string with all
|
|
|
+uppercase letters changed to lowercase.
|
|
|
+All other characters are left unchanged.
|
|
|
+The definition of what an uppercase letter is depends on the current locale.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.match (s, pattern [, init])|
|
|
|
+Looks for the first @emph{match} of
|
|
|
+@id{pattern} @see{pm} in the string @id{s}.
|
|
|
+If it finds one, then @id{match} returns
|
|
|
+the captures from the pattern;
|
|
|
+otherwise it returns @nil.
|
|
|
+If @id{pattern} specifies no captures,
|
|
|
+then the whole match is returned.
|
|
|
+A third, optional numeric argument @id{init} specifies
|
|
|
+where to start the search;
|
|
|
+its default value @N{is 1} and can be negative.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.pack (fmt, v1, v2, @Cdots)|
|
|
|
+
|
|
|
+Returns a binary string containing the values @id{v1}, @id{v2}, etc.
|
|
|
+packed (that is, serialized in binary form)
|
|
|
+according to the format string @id{fmt} @see{pack}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.packsize (fmt)|
|
|
|
+
|
|
|
+Returns the size of a string resulting from @Lid{string.pack}
|
|
|
+with the given format.
|
|
|
+The format string cannot have the variable-length options
|
|
|
+@Char{s} or @Char{z} @see{pack}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.rep (s, n [, sep])|
|
|
|
+Returns a string that is the concatenation of @id{n} copies of
|
|
|
+the string @id{s} separated by the string @id{sep}.
|
|
|
+The default value for @id{sep} is the empty string
|
|
|
+(that is, no separator).
|
|
|
+Returns the empty string if @id{n} is not positive.
|
|
|
+
|
|
|
+(Note that it is very easy to exhaust the memory of your machine
|
|
|
+with a single call to this function.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.reverse (s)|
|
|
|
+Returns a string that is the string @id{s} reversed.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.sub (s, i [, j])|
|
|
|
+Returns the substring of @id{s} that
|
|
|
+starts at @id{i} and continues until @id{j};
|
|
|
+@id{i} and @id{j} can be negative.
|
|
|
+If @id{j} is absent, then it is assumed to be equal to @num{-1}
|
|
|
+(which is the same as the string length).
|
|
|
+In particular,
|
|
|
+the call @T{string.sub(s,1,j)} returns a prefix of @id{s}
|
|
|
+with length @id{j},
|
|
|
+and @T{string.sub(s, -i)} (for a positive @id{i})
|
|
|
+returns a suffix of @id{s}
|
|
|
+with length @id{i}.
|
|
|
+
|
|
|
+If, after the translation of negative indices,
|
|
|
+@id{i} is less than 1,
|
|
|
+it is corrected to 1.
|
|
|
+If @id{j} is greater than the string length,
|
|
|
+it is corrected to that length.
|
|
|
+If, after these corrections,
|
|
|
+@id{i} is greater than @id{j},
|
|
|
+the function returns the empty string.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.unpack (fmt, s [, pos])|
|
|
|
+
|
|
|
+Returns the values packed in string @id{s} @seeF{string.pack}
|
|
|
+according to the format string @id{fmt} @see{pack}.
|
|
|
+An optional @id{pos} marks where
|
|
|
+to start reading in @id{s} (default is 1).
|
|
|
+After the read values,
|
|
|
+this function also returns the index of the first unread byte in @id{s}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{string.upper (s)|
|
|
|
+Receives a string and returns a copy of this string with all
|
|
|
+lowercase letters changed to uppercase.
|
|
|
+All other characters are left unchanged.
|
|
|
+The definition of what a lowercase letter is depends on the current locale.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@sect3{pm| @title{Patterns}
|
|
|
+
|
|
|
+Patterns in Lua are described by regular strings,
|
|
|
+which are interpreted as patterns by the pattern-matching functions
|
|
|
+@Lid{string.find},
|
|
|
+@Lid{string.gmatch},
|
|
|
+@Lid{string.gsub},
|
|
|
+and @Lid{string.match}.
|
|
|
+This section describes the syntax and the meaning
|
|
|
+(that is, what they match) of these strings.
|
|
|
+
|
|
|
+@sect4{@title{Character Class:}
|
|
|
+A @def{character class} is used to represent a set of characters.
|
|
|
+The following combinations are allowed in describing a character class:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@rep{x}|
|
|
|
+(where @rep{x} is not one of the @emphx{magic characters}
|
|
|
+@T{^$()%.[]*+-?})
|
|
|
+represents the character @emph{x} itself.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@T{.}| (a dot) represents all characters.}
|
|
|
+
|
|
|
+@item{@T{%a}| represents all letters.}
|
|
|
+
|
|
|
+@item{@T{%c}| represents all control characters.}
|
|
|
+
|
|
|
+@item{@T{%d}| represents all digits.}
|
|
|
+
|
|
|
+@item{@T{%g}| represents all printable characters except space.}
|
|
|
+
|
|
|
+@item{@T{%l}| represents all lowercase letters.}
|
|
|
+
|
|
|
+@item{@T{%p}| represents all punctuation characters.}
|
|
|
+
|
|
|
+@item{@T{%s}| represents all space characters.}
|
|
|
+
|
|
|
+@item{@T{%u}| represents all uppercase letters.}
|
|
|
+
|
|
|
+@item{@T{%w}| represents all alphanumeric characters.}
|
|
|
+
|
|
|
+@item{@T{%x}| represents all hexadecimal digits.}
|
|
|
+
|
|
|
+@item{@T{%@rep{x}}| (where @rep{x} is any non-alphanumeric character)
|
|
|
+represents the character @rep{x}.
|
|
|
+This is the standard way to escape the magic characters.
|
|
|
+Any non-alphanumeric character
|
|
|
+(including all punctuation characters, even the non-magical)
|
|
|
+can be preceded by a @Char{%}
|
|
|
+when used to represent itself in a pattern.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@T{[@rep{set}]}|
|
|
|
+represents the class which is the union of all
|
|
|
+characters in @rep{set}.
|
|
|
+A range of characters can be specified by
|
|
|
+separating the end characters of the range,
|
|
|
+in ascending order, with a @Char{-}.
|
|
|
+All classes @T{%}@emph{x} described above can also be used as
|
|
|
+components in @rep{set}.
|
|
|
+All other characters in @rep{set} represent themselves.
|
|
|
+For example, @T{[%w_]} (or @T{[_%w]})
|
|
|
+represents all alphanumeric characters plus the underscore,
|
|
|
+@T{[0-7]} represents the octal digits,
|
|
|
+and @T{[0-7%l%-]} represents the octal digits plus
|
|
|
+the lowercase letters plus the @Char{-} character.
|
|
|
+
|
|
|
+You can put a closing square bracket in a set
|
|
|
+by positioning it as the first character in the set.
|
|
|
+You can put a hyphen in a set
|
|
|
+by positioning it as the first or the last character in the set.
|
|
|
+(You can also use an escape for both cases.)
|
|
|
+
|
|
|
+The interaction between ranges and classes is not defined.
|
|
|
+Therefore, patterns like @T{[%a-z]} or @T{[a-%%]}
|
|
|
+have no meaning.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@T{[^@rep{set}]}|
|
|
|
+represents the complement of @rep{set},
|
|
|
+where @rep{set} is interpreted as above.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+For all classes represented by single letters (@T{%a}, @T{%c}, etc.),
|
|
|
+the corresponding uppercase letter represents the complement of the class.
|
|
|
+For instance, @T{%S} represents all non-space characters.
|
|
|
+
|
|
|
+The definitions of letter, space, and other character groups
|
|
|
+depend on the current locale.
|
|
|
+In particular, the class @T{[a-z]} may not be equivalent to @T{%l}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect4{@title{Pattern Item:}
|
|
|
+A @def{pattern item} can be
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{
|
|
|
+a single character class,
|
|
|
+which matches any single character in the class;
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+a single character class followed by @Char{*},
|
|
|
+which matches zero or more repetitions of characters in the class.
|
|
|
+These repetition items will always match the longest possible sequence;
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+a single character class followed by @Char{+},
|
|
|
+which matches one or more repetitions of characters in the class.
|
|
|
+These repetition items will always match the longest possible sequence;
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+a single character class followed by @Char{-},
|
|
|
+which also matches zero or more repetitions of characters in the class.
|
|
|
+Unlike @Char{*},
|
|
|
+these repetition items will always match the shortest possible sequence;
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+a single character class followed by @Char{?},
|
|
|
+which matches zero or one occurrence of a character in the class.
|
|
|
+It always matches one occurrence if possible;
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+@T{%@rep{n}}, for @rep{n} between 1 and 9;
|
|
|
+such item matches a substring equal to the @rep{n}-th captured string
|
|
|
+(see below);
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+@T{%b@rep{xy}}, where @rep{x} and @rep{y} are two distinct characters;
|
|
|
+such item matches strings that start @N{with @rep{x}}, end @N{with @rep{y}},
|
|
|
+and where the @rep{x} and @rep{y} are @emph{balanced}.
|
|
|
+This means that, if one reads the string from left to right,
|
|
|
+counting @M{+1} for an @rep{x} and @M{-1} for a @rep{y},
|
|
|
+the ending @rep{y} is the first @rep{y} where the count reaches 0.
|
|
|
+For instance, the item @T{%b()} matches expressions with
|
|
|
+balanced parentheses.
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+@T{%f[@rep{set}]}, a @def{frontier pattern};
|
|
|
+such item matches an empty string at any position such that
|
|
|
+the next character belongs to @rep{set}
|
|
|
+and the previous character does not belong to @rep{set}.
|
|
|
+The set @rep{set} is interpreted as previously described.
|
|
|
+The beginning and the end of the subject are handled as if
|
|
|
+they were the character @Char{\0}.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect4{@title{Pattern:}
|
|
|
+A @def{pattern} is a sequence of pattern items.
|
|
|
+A caret @Char{^} at the beginning of a pattern anchors the match at the
|
|
|
+beginning of the subject string.
|
|
|
+A @Char{$} at the end of a pattern anchors the match at the
|
|
|
+end of the subject string.
|
|
|
+At other positions,
|
|
|
+@Char{^} and @Char{$} have no special meaning and represent themselves.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect4{@title{Captures:}
|
|
|
+A pattern can contain sub-patterns enclosed in parentheses;
|
|
|
+they describe @def{captures}.
|
|
|
+When a match succeeds, the substrings of the subject string
|
|
|
+that match captures are stored (@emph{captured}) for future use.
|
|
|
+Captures are numbered according to their left parentheses.
|
|
|
+For instance, in the pattern @T{"(a*(.)%w(%s*))"},
|
|
|
+the part of the string matching @T{"a*(.)%w(%s*)"} is
|
|
|
+stored as the first capture (and therefore has @N{number 1});
|
|
|
+the character matching @St{.} is captured with @N{number 2},
|
|
|
+and the part matching @St{%s*} has @N{number 3}.
|
|
|
+
|
|
|
+As a special case, the empty capture @T{()} captures
|
|
|
+the current string position (a number).
|
|
|
+For instance, if we apply the pattern @T{"()aa()"} on the
|
|
|
+string @T{"flaaap"}, there will be two captures: @N{3 and 5}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect4{@title{Multiple matches:}
|
|
|
+The function @Lid{string.gsub} and the iterator @Lid{string.gmatch}
|
|
|
+match multiple occurrences of the given pattern in the subject.
|
|
|
+For these functions,
|
|
|
+a new match is considered valid only
|
|
|
+if it ends at least one byte after the previous match.
|
|
|
+In other words, the pattern machine never accepts the
|
|
|
+empty string as a match immediately after another match.
|
|
|
+As an example,
|
|
|
+consider the results of the following code:
|
|
|
+@verbatim{
|
|
|
+> string.gsub("abc", "()a*()", print)
|
|
|
+--> 1 2
|
|
|
+--> 3 3
|
|
|
+--> 4 4
|
|
|
+}
|
|
|
+The second and third results come from Lua matching an empty
|
|
|
+string after @Char{b} and another one after @Char{c}.
|
|
|
+Lua does not match an empty string after @Char{a},
|
|
|
+because it would end at the same position of the previous match.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect3{pack| @title{Format Strings for Pack and Unpack}
|
|
|
+
|
|
|
+The first argument to @Lid{string.pack},
|
|
|
+@Lid{string.packsize}, and @Lid{string.unpack}
|
|
|
+is a format string,
|
|
|
+which describes the layout of the structure being created or read.
|
|
|
+
|
|
|
+A format string is a sequence of conversion options.
|
|
|
+The conversion options are as follows:
|
|
|
+@description{
|
|
|
+@item{@T{<}|sets little endian}
|
|
|
+@item{@T{>}|sets big endian}
|
|
|
+@item{@T{=}|sets native endian}
|
|
|
+@item{@T{![@rep{n}]}|sets maximum alignment to @id{n}
|
|
|
+(default is native alignment)}
|
|
|
+@item{@T{b}|a signed byte (@id{char})}
|
|
|
+@item{@T{B}|an unsigned byte (@id{char})}
|
|
|
+@item{@T{h}|a signed @id{short} (native size)}
|
|
|
+@item{@T{H}|an unsigned @id{short} (native size)}
|
|
|
+@item{@T{l}|a signed @id{long} (native size)}
|
|
|
+@item{@T{L}|an unsigned @id{long} (native size)}
|
|
|
+@item{@T{j}|a @id{lua_Integer}}
|
|
|
+@item{@T{J}|a @id{lua_Unsigned}}
|
|
|
+@item{@T{T}|a @id{size_t} (native size)}
|
|
|
+@item{@T{i[@rep{n}]}|a signed @id{int} with @id{n} bytes
|
|
|
+(default is native size)}
|
|
|
+@item{@T{I[@rep{n}]}|an unsigned @id{int} with @id{n} bytes
|
|
|
+(default is native size)}
|
|
|
+@item{@T{f}|a @id{float} (native size)}
|
|
|
+@item{@T{d}|a @id{double} (native size)}
|
|
|
+@item{@T{n}|a @id{lua_Number}}
|
|
|
+@item{@T{c@rep{n}}|a fixed-sized string with @id{n} bytes}
|
|
|
+@item{@T{z}|a zero-terminated string}
|
|
|
+@item{@T{s[@emph{n}]}|a string preceded by its length
|
|
|
+coded as an unsigned integer with @id{n} bytes
|
|
|
+(default is a @id{size_t})}
|
|
|
+@item{@T{x}|one byte of padding}
|
|
|
+@item{@T{X@rep{op}}|an empty item that aligns
|
|
|
+according to option @id{op}
|
|
|
+(which is otherwise ignored)}
|
|
|
+@item{@Char{ }|(empty space) ignored}
|
|
|
+}
|
|
|
+(A @St{[@rep{n}]} means an optional integral numeral.)
|
|
|
+Except for padding, spaces, and configurations
|
|
|
+(options @St{xX <=>!}),
|
|
|
+each option corresponds to an argument (in @Lid{string.pack})
|
|
|
+or a result (in @Lid{string.unpack}).
|
|
|
+
|
|
|
+For options @St{!@rep{n}}, @St{s@rep{n}}, @St{i@rep{n}}, and @St{I@rep{n}},
|
|
|
+@id{n} can be any integer between 1 and 16.
|
|
|
+All integral options check overflows;
|
|
|
+@Lid{string.pack} checks whether the given value fits in the given size;
|
|
|
+@Lid{string.unpack} checks whether the read value fits in a Lua integer.
|
|
|
+
|
|
|
+Any format string starts as if prefixed by @St{!1=},
|
|
|
+that is,
|
|
|
+with maximum alignment of 1 (no alignment)
|
|
|
+and native endianness.
|
|
|
+
|
|
|
+Alignment works as follows:
|
|
|
+For each option,
|
|
|
+the format gets extra padding until the data starts
|
|
|
+at an offset that is a multiple of the minimum between the
|
|
|
+option size and the maximum alignment;
|
|
|
+this minimum must be a power of 2.
|
|
|
+Options @St{c} and @St{z} are not aligned;
|
|
|
+option @St{s} follows the alignment of its starting integer.
|
|
|
+
|
|
|
+All padding is filled with zeros by @Lid{string.pack}
|
|
|
+(and ignored by @Lid{string.unpack}).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{utf8| @title{UTF-8 Support}
|
|
|
+
|
|
|
+This library provides basic support for @x{UTF-8} encoding.
|
|
|
+It provides all its functions inside the table @defid{utf8}.
|
|
|
+This library does not provide any support for @x{Unicode} other
|
|
|
+than the handling of the encoding.
|
|
|
+Any operation that needs the meaning of a character,
|
|
|
+such as character classification, is outside its scope.
|
|
|
+
|
|
|
+Unless stated otherwise,
|
|
|
+all functions that expect a byte position as a parameter
|
|
|
+assume that the given position is either the start of a byte sequence
|
|
|
+or one plus the length of the subject string.
|
|
|
+As in the string library,
|
|
|
+negative indices count from the end of the string.
|
|
|
+
|
|
|
+
|
|
|
+@LibEntry{utf8.char (@Cdots)|
|
|
|
+Receives zero or more integers,
|
|
|
+converts each one to its corresponding UTF-8 byte sequence
|
|
|
+and returns a string with the concatenation of all these sequences.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{utf8.charpattern|
|
|
|
+The pattern (a string, not a function) @St{[\0-\x7F\xC2-\xF4][\x80-\xBF]*}
|
|
|
+@see{pm},
|
|
|
+which matches exactly one UTF-8 byte sequence,
|
|
|
+assuming that the subject is a valid UTF-8 string.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{utf8.codes (s)|
|
|
|
+
|
|
|
+Returns values so that the construction
|
|
|
+@verbatim{
|
|
|
+for p, c in utf8.codes(s) do @rep{body} end
|
|
|
+}
|
|
|
+will iterate over all characters in string @id{s},
|
|
|
+with @id{p} being the position (in bytes) and @id{c} the code point
|
|
|
+of each character.
|
|
|
+It raises an error if it meets any invalid byte sequence.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{utf8.codepoint (s [, i [, j]])|
|
|
|
+Returns the codepoints (as integers) from all characters in @id{s}
|
|
|
+that start between byte position @id{i} and @id{j} (both included).
|
|
|
+The default for @id{i} is 1 and for @id{j} is @id{i}.
|
|
|
+It raises an error if it meets any invalid byte sequence.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{utf8.len (s [, i [, j]])|
|
|
|
+Returns the number of UTF-8 characters in string @id{s}
|
|
|
+that start between positions @id{i} and @id{j} (both inclusive).
|
|
|
+The default for @id{i} is @num{1} and for @id{j} is @num{-1}.
|
|
|
+If it finds any invalid byte sequence,
|
|
|
+returns a false value plus the position of the first invalid byte.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{utf8.offset (s, n [, i])|
|
|
|
+Returns the position (in bytes) where the encoding of the
|
|
|
+@id{n}-th character of @id{s}
|
|
|
+(counting from position @id{i}) starts.
|
|
|
+A negative @id{n} gets characters before position @id{i}.
|
|
|
+The default for @id{i} is 1 when @id{n} is non-negative
|
|
|
+and @T{#s + 1} otherwise,
|
|
|
+so that @T{utf8.offset(s, -n)} gets the offset of the
|
|
|
+@id{n}-th character from the end of the string.
|
|
|
+If the specified character is neither in the subject
|
|
|
+nor right after its end,
|
|
|
+the function returns @nil.
|
|
|
+
|
|
|
+As a special case,
|
|
|
+when @id{n} is 0 the function returns the start of the encoding
|
|
|
+of the character that contains the @id{i}-th byte of @id{s}.
|
|
|
+
|
|
|
+This function assumes that @id{s} is a valid UTF-8 string.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{tablib| @title{Table Manipulation}
|
|
|
+
|
|
|
+This library provides generic functions for table manipulation.
|
|
|
+It provides all its functions inside the table @defid{table}.
|
|
|
+
|
|
|
+Remember that, whenever an operation needs the length of a table,
|
|
|
+all caveats about the length operator apply @see{len-op}.
|
|
|
+All functions ignore non-numeric keys
|
|
|
+in the tables given as arguments.
|
|
|
+
|
|
|
+
|
|
|
+@LibEntry{table.concat (list [, sep [, i [, j]]])|
|
|
|
+
|
|
|
+Given a list where all elements are strings or numbers,
|
|
|
+returns the string @T{list[i]..sep..list[i+1] @Cdots sep..list[j]}.
|
|
|
+The default value for @id{sep} is the empty string,
|
|
|
+the default for @id{i} is 1,
|
|
|
+and the default for @id{j} is @T{#list}.
|
|
|
+If @id{i} is greater than @id{j}, returns the empty string.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{table.insert (list, [pos,] value)|
|
|
|
+
|
|
|
+Inserts element @id{value} at position @id{pos} in @id{list},
|
|
|
+shifting up the elements
|
|
|
+@T{list[pos], list[pos+1], @Cdots, list[#list]}.
|
|
|
+The default value for @id{pos} is @T{#list+1},
|
|
|
+so that a call @T{table.insert(t,x)} inserts @id{x} at the end
|
|
|
+of list @id{t}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{table.move (a1, f, e, t [,a2])|
|
|
|
+
|
|
|
+Moves elements from table @id{a1} to table @id{a2},
|
|
|
+performing the equivalent to the following
|
|
|
+multiple assignment:
|
|
|
+@T{a2[t],@Cdots = a1[f],@Cdots,a1[e]}.
|
|
|
+The default for @id{a2} is @id{a1}.
|
|
|
+The destination range can overlap with the source range.
|
|
|
+The number of elements to be moved must fit in a Lua integer.
|
|
|
+
|
|
|
+Returns the destination table @id{a2}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{table.pack (@Cdots)|
|
|
|
+
|
|
|
+Returns a new table with all arguments stored into keys 1, 2, etc.
|
|
|
+and with a field @St{n} with the total number of arguments.
|
|
|
+Note that the resulting table may not be a sequence,
|
|
|
+if some arguments are @nil.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{table.remove (list [, pos])|
|
|
|
+
|
|
|
+Removes from @id{list} the element at position @id{pos},
|
|
|
+returning the value of the removed element.
|
|
|
+When @id{pos} is an integer between 1 and @T{#list},
|
|
|
+it shifts down the elements
|
|
|
+@T{list[pos+1], list[pos+2], @Cdots, list[#list]}
|
|
|
+and erases element @T{list[#list]};
|
|
|
+The index @id{pos} can also be 0 when @T{#list} is 0,
|
|
|
+or @T{#list + 1}.
|
|
|
+
|
|
|
+The default value for @id{pos} is @T{#list},
|
|
|
+so that a call @T{table.remove(l)} removes the last element
|
|
|
+of list @id{l}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{table.sort (list [, comp])|
|
|
|
+
|
|
|
+Sorts list elements in a given order, @emph{in-place},
|
|
|
+from @T{list[1]} to @T{list[#list]}.
|
|
|
+If @id{comp} is given,
|
|
|
+then it must be a function that receives two list elements
|
|
|
+and returns true when the first element must come
|
|
|
+before the second in the final order
|
|
|
+(so that, after the sort,
|
|
|
+@T{i < j} implies @T{not comp(list[j],list[i])}).
|
|
|
+If @id{comp} is not given,
|
|
|
+then the standard Lua operator @T{<} is used instead.
|
|
|
+
|
|
|
+Note that the @id{comp} function must define
|
|
|
+a strict partial order over the elements in the list;
|
|
|
+that is, it must be asymmetric and transitive.
|
|
|
+Otherwise, no valid sort may be possible.
|
|
|
+
|
|
|
+The sort algorithm is not stable:
|
|
|
+elements considered equal by the given order
|
|
|
+may have their relative positions changed by the sort.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{table.unpack (list [, i [, j]])|
|
|
|
+
|
|
|
+Returns the elements from the given list.
|
|
|
+This function is equivalent to
|
|
|
+@verbatim{
|
|
|
+return list[i], list[i+1], @Cdots, list[j]
|
|
|
+}
|
|
|
+By default, @id{i} @N{is 1} and @id{j} is @T{#list}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{mathlib| @title{Mathematical Functions}
|
|
|
+
|
|
|
+This library provides basic mathematical functions.
|
|
|
+It provides all its functions and constants inside the table @defid{math}.
|
|
|
+Functions with the annotation @St{integer/float} give
|
|
|
+integer results for integer arguments
|
|
|
+and float results for float (or mixed) arguments.
|
|
|
+Rounding functions
|
|
|
+(@Lid{math.ceil}, @Lid{math.floor}, and @Lid{math.modf})
|
|
|
+return an integer when the result fits in the range of an integer,
|
|
|
+or a float otherwise.
|
|
|
+
|
|
|
+@LibEntry{math.abs (x)|
|
|
|
+
|
|
|
+Returns the absolute value of @id{x}. (integer/float)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.acos (x)|
|
|
|
+
|
|
|
+Returns the arc cosine of @id{x} (in radians).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.asin (x)|
|
|
|
+
|
|
|
+Returns the arc sine of @id{x} (in radians).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.atan (y [, x])|
|
|
|
+
|
|
|
+@index{atan2}
|
|
|
+Returns the arc tangent of @T{y/x} (in radians),
|
|
|
+but uses the signs of both parameters to find the
|
|
|
+quadrant of the result.
|
|
|
+(It also handles correctly the case of @id{x} being zero.)
|
|
|
+
|
|
|
+The default value for @id{x} is 1,
|
|
|
+so that the call @T{math.atan(y)}
|
|
|
+returns the arc tangent of @id{y}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.ceil (x)|
|
|
|
+
|
|
|
+Returns the smallest integral value larger than or equal to @id{x}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.cos (x)|
|
|
|
+
|
|
|
+Returns the cosine of @id{x} (assumed to be in radians).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.deg (x)|
|
|
|
+
|
|
|
+Converts the angle @id{x} from radians to degrees.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.exp (x)|
|
|
|
+
|
|
|
+Returns the value @M{e@sp{x}}
|
|
|
+(where @id{e} is the base of natural logarithms).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.floor (x)|
|
|
|
+
|
|
|
+Returns the largest integral value smaller than or equal to @id{x}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.fmod (x, y)|
|
|
|
+
|
|
|
+Returns the remainder of the division of @id{x} by @id{y}
|
|
|
+that rounds the quotient towards zero. (integer/float)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.huge|
|
|
|
+
|
|
|
+The float value @idx{HUGE_VAL},
|
|
|
+a value larger than any other numeric value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.log (x [, base])|
|
|
|
+
|
|
|
+Returns the logarithm of @id{x} in the given base.
|
|
|
+The default for @id{base} is @M{e}
|
|
|
+(so that the function returns the natural logarithm of @id{x}).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.max (x, @Cdots)|
|
|
|
+
|
|
|
+Returns the argument with the maximum value,
|
|
|
+according to the Lua operator @T{<}. (integer/float)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.maxinteger|
|
|
|
+An integer with the maximum value for an integer.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.min (x, @Cdots)|
|
|
|
+
|
|
|
+Returns the argument with the minimum value,
|
|
|
+according to the Lua operator @T{<}. (integer/float)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.mininteger|
|
|
|
+An integer with the minimum value for an integer.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.modf (x)|
|
|
|
+
|
|
|
+Returns the integral part of @id{x} and the fractional part of @id{x}.
|
|
|
+Its second result is always a float.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.pi|
|
|
|
+
|
|
|
+The value of @M{@pi}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.rad (x)|
|
|
|
+
|
|
|
+Converts the angle @id{x} from degrees to radians.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.random ([m [, n]])|
|
|
|
+
|
|
|
+When called without arguments,
|
|
|
+returns a pseudo-random float with uniform distribution
|
|
|
+in the range @C{(} @M{[0,1)}. @C{]}
|
|
|
+When called with two integers @id{m} and @id{n},
|
|
|
+@id{math.random} returns a pseudo-random integer
|
|
|
+with uniform distribution in the range @M{[m, n]}.
|
|
|
+The call @T{math.random(n)}, for a positive @id{n},
|
|
|
+is equivalent to @T{math.random(1,n)}.
|
|
|
+The call @T{math.random(0)} produces an integer with
|
|
|
+all bits (pseudo)random.
|
|
|
+
|
|
|
+Lua initializes its pseudo-random generator with
|
|
|
+a weak attempt for ``randomness'',
|
|
|
+so that @id{math.random} should generate
|
|
|
+different sequences of results each time the program runs.
|
|
|
+To ensure a required level of randomness to the initial state
|
|
|
+(or contrarily, to have a deterministic sequence,
|
|
|
+for instance when debugging a program),
|
|
|
+you should call @Lid{math.randomseed} explicitly.
|
|
|
+
|
|
|
+The results from this function have good statistical qualities,
|
|
|
+but they are not cryptographically secure.
|
|
|
+(For instance, there are no garanties that it is hard
|
|
|
+to predict future results based on the observation of
|
|
|
+some number of previous results.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.randomseed (x [, y])|
|
|
|
+
|
|
|
+Sets @id{x} and @id{y} as the @Q{seed}
|
|
|
+for the pseudo-random generator:
|
|
|
+equal seeds produce equal sequences of numbers.
|
|
|
+The default for @id{y} is zero.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.sin (x)|
|
|
|
+
|
|
|
+Returns the sine of @id{x} (assumed to be in radians).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.sqrt (x)|
|
|
|
+
|
|
|
+Returns the square root of @id{x}.
|
|
|
+(You can also use the expression @T{x^0.5} to compute this value.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.tan (x)|
|
|
|
+
|
|
|
+Returns the tangent of @id{x} (assumed to be in radians).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.tointeger (x)|
|
|
|
+
|
|
|
+If the value @id{x} is convertible to an integer,
|
|
|
+returns that integer.
|
|
|
+Otherwise, returns @nil.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.type (x)|
|
|
|
+
|
|
|
+Returns @St{integer} if @id{x} is an integer,
|
|
|
+@St{float} if it is a float,
|
|
|
+or @nil if @id{x} is not a number.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{math.ult (m, n)|
|
|
|
+
|
|
|
+Returns a boolean,
|
|
|
+true if and only if integer @id{m} is below integer @id{n} when
|
|
|
+they are compared as @x{unsigned integers}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@sect2{iolib| @title{Input and Output Facilities}
|
|
|
+
|
|
|
+The I/O library provides two different styles for file manipulation.
|
|
|
+The first one uses implicit file handles;
|
|
|
+that is, there are operations to set a default input file and a
|
|
|
+default output file,
|
|
|
+and all input/output operations are over these default files.
|
|
|
+The second style uses explicit file handles.
|
|
|
+
|
|
|
+When using implicit file handles,
|
|
|
+all operations are supplied by table @defid{io}.
|
|
|
+When using explicit file handles,
|
|
|
+the operation @Lid{io.open} returns a file handle
|
|
|
+and then all operations are supplied as methods of the file handle.
|
|
|
+
|
|
|
+The table @id{io} also provides
|
|
|
+three predefined file handles with their usual meanings from C:
|
|
|
+@defid{io.stdin}, @defid{io.stdout}, and @defid{io.stderr}.
|
|
|
+The I/O library never closes these files.
|
|
|
+
|
|
|
+Unless otherwise stated,
|
|
|
+all I/O functions return @nil on failure
|
|
|
+(plus an error message as a second result and
|
|
|
+a system-dependent error code as a third result)
|
|
|
+and some value different from @nil on success.
|
|
|
+On non-POSIX systems,
|
|
|
+the computation of the error message and error code
|
|
|
+in case of errors
|
|
|
+may be not @x{thread safe},
|
|
|
+because they rely on the global C variable @id{errno}.
|
|
|
+
|
|
|
+@LibEntry{io.close ([file])|
|
|
|
+
|
|
|
+Equivalent to @T{file:close()}.
|
|
|
+Without a @id{file}, closes the default output file.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.flush ()|
|
|
|
+
|
|
|
+Equivalent to @T{io.output():flush()}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.input ([file])|
|
|
|
+
|
|
|
+When called with a file name, it opens the named file (in text mode),
|
|
|
+and sets its handle as the default input file.
|
|
|
+When called with a file handle,
|
|
|
+it simply sets this file handle as the default input file.
|
|
|
+When called without parameters,
|
|
|
+it returns the current default input file.
|
|
|
+
|
|
|
+In case of errors this function raises the error,
|
|
|
+instead of returning an error code.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.lines ([filename, @Cdots])|
|
|
|
+
|
|
|
+Opens the given file name in read mode
|
|
|
+and returns an iterator function that
|
|
|
+works like @T{file:lines(@Cdots)} over the opened file.
|
|
|
+When the iterator function detects the end of file,
|
|
|
+it returns no values (to finish the loop) and automatically closes the file.
|
|
|
+
|
|
|
+The call @T{io.lines()} (with no file name) is equivalent
|
|
|
+to @T{io.input():lines("l")};
|
|
|
+that is, it iterates over the lines of the default input file.
|
|
|
+In this case, the iterator does not close the file when the loop ends.
|
|
|
+
|
|
|
+In case of errors this function raises the error,
|
|
|
+instead of returning an error code.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.open (filename [, mode])|
|
|
|
+
|
|
|
+This function opens a file,
|
|
|
+in the mode specified in the string @id{mode}.
|
|
|
+In case of success,
|
|
|
+it returns a new file handle.
|
|
|
+
|
|
|
+The @id{mode} string can be any of the following:
|
|
|
+@description{
|
|
|
+@item{@St{r}| read mode (the default);}
|
|
|
+@item{@St{w}| write mode;}
|
|
|
+@item{@St{a}| append mode;}
|
|
|
+@item{@St{r+}| update mode, all previous data is preserved;}
|
|
|
+@item{@St{w+}| update mode, all previous data is erased;}
|
|
|
+@item{@St{a+}| append update mode, previous data is preserved,
|
|
|
+ writing is only allowed at the end of file.}
|
|
|
+}
|
|
|
+The @id{mode} string can also have a @Char{b} at the end,
|
|
|
+which is needed in some systems to open the file in binary mode.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.output ([file])|
|
|
|
+
|
|
|
+Similar to @Lid{io.input}, but operates over the default output file.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.popen (prog [, mode])|
|
|
|
+
|
|
|
+This function is system dependent and is not available
|
|
|
+on all platforms.
|
|
|
+
|
|
|
+Starts program @id{prog} in a separated process and returns
|
|
|
+a file handle that you can use to read data from this program
|
|
|
+(if @id{mode} is @T{"r"}, the default)
|
|
|
+or to write data to this program
|
|
|
+(if @id{mode} is @T{"w"}).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.read (@Cdots)|
|
|
|
+
|
|
|
+Equivalent to @T{io.input():read(@Cdots)}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.tmpfile ()|
|
|
|
+
|
|
|
+In case of success,
|
|
|
+returns a handle for a temporary file.
|
|
|
+This file is opened in update mode
|
|
|
+and it is automatically removed when the program ends.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.type (obj)|
|
|
|
+
|
|
|
+Checks whether @id{obj} is a valid file handle.
|
|
|
+Returns the string @T{"file"} if @id{obj} is an open file handle,
|
|
|
+@T{"closed file"} if @id{obj} is a closed file handle,
|
|
|
+or @nil if @id{obj} is not a file handle.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{io.write (@Cdots)|
|
|
|
+
|
|
|
+Equivalent to @T{io.output():write(@Cdots)}.
|
|
|
+
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{file:close ()|
|
|
|
+
|
|
|
+Closes @id{file}.
|
|
|
+Note that files are automatically closed when
|
|
|
+their handles are garbage collected,
|
|
|
+but that takes an unpredictable amount of time to happen.
|
|
|
+
|
|
|
+When closing a file handle created with @Lid{io.popen},
|
|
|
+@Lid{file:close} returns the same values
|
|
|
+returned by @Lid{os.execute}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{file:flush ()|
|
|
|
+
|
|
|
+Saves any written data to @id{file}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{file:lines (@Cdots)|
|
|
|
+
|
|
|
+Returns an iterator function that,
|
|
|
+each time it is called,
|
|
|
+reads the file according to the given formats.
|
|
|
+When no format is given,
|
|
|
+uses @St{l} as a default.
|
|
|
+As an example, the construction
|
|
|
+@verbatim{
|
|
|
+for c in file:lines(1) do @rep{body} end
|
|
|
+}
|
|
|
+will iterate over all characters of the file,
|
|
|
+starting at the current position.
|
|
|
+Unlike @Lid{io.lines}, this function does not close the file
|
|
|
+when the loop ends.
|
|
|
+
|
|
|
+In case of errors this function raises the error,
|
|
|
+instead of returning an error code.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{file:read (@Cdots)|
|
|
|
+
|
|
|
+Reads the file @id{file},
|
|
|
+according to the given formats, which specify what to read.
|
|
|
+For each format,
|
|
|
+the function returns a string or a number with the characters read,
|
|
|
+or @nil if it cannot read data with the specified format.
|
|
|
+(In this latter case,
|
|
|
+the function does not read subsequent formats.)
|
|
|
+When called without parameters,
|
|
|
+it uses a default format that reads the next line
|
|
|
+(see below).
|
|
|
+
|
|
|
+The available formats are
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@St{n}|
|
|
|
+reads a numeral and returns it as a float or an integer,
|
|
|
+following the lexical conventions of Lua.
|
|
|
+(The numeral may have leading spaces and a sign.)
|
|
|
+This format always reads the longest input sequence that
|
|
|
+is a valid prefix for a numeral;
|
|
|
+if that prefix does not form a valid numeral
|
|
|
+(e.g., an empty string, @St{0x}, or @St{3.4e-}),
|
|
|
+it is discarded and the format returns @nil.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{a}|
|
|
|
+reads the whole file, starting at the current position.
|
|
|
+On end of file, it returns the empty string.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{l}|
|
|
|
+reads the next line skipping the end of line,
|
|
|
+returning @nil on end of file.
|
|
|
+This is the default format.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{L}|
|
|
|
+reads the next line keeping the end-of-line character (if present),
|
|
|
+returning @nil on end of file.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@emph{number}|
|
|
|
+reads a string with up to this number of bytes,
|
|
|
+returning @nil on end of file.
|
|
|
+If @id{number} is zero,
|
|
|
+it reads nothing and returns an empty string,
|
|
|
+or @nil on end of file.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+The formats @St{l} and @St{L} should be used only for text files.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{file:seek ([whence [, offset]])|
|
|
|
+
|
|
|
+Sets and gets the file position,
|
|
|
+measured from the beginning of the file,
|
|
|
+to the position given by @id{offset} plus a base
|
|
|
+specified by the string @id{whence}, as follows:
|
|
|
+@description{
|
|
|
+@item{@St{set}| base is position 0 (beginning of the file);}
|
|
|
+@item{@St{cur}| base is current position;}
|
|
|
+@item{@St{end}| base is end of file;}
|
|
|
+}
|
|
|
+In case of success, @id{seek} returns the final file position,
|
|
|
+measured in bytes from the beginning of the file.
|
|
|
+If @id{seek} fails, it returns @nil,
|
|
|
+plus a string describing the error.
|
|
|
+
|
|
|
+The default value for @id{whence} is @T{"cur"},
|
|
|
+and for @id{offset} is 0.
|
|
|
+Therefore, the call @T{file:seek()} returns the current
|
|
|
+file position, without changing it;
|
|
|
+the call @T{file:seek("set")} sets the position to the
|
|
|
+beginning of the file (and returns 0);
|
|
|
+and the call @T{file:seek("end")} sets the position to the
|
|
|
+end of the file, and returns its size.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{file:setvbuf (mode [, size])|
|
|
|
+
|
|
|
+Sets the buffering mode for an output file.
|
|
|
+There are three available modes:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@St{no}|
|
|
|
+no buffering; the result of any output operation appears immediately.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{full}|
|
|
|
+full buffering; output operation is performed only
|
|
|
+when the buffer is full or when
|
|
|
+you explicitly @T{flush} the file @seeF{io.flush}.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{line}|
|
|
|
+line buffering; output is buffered until a newline is output
|
|
|
+or there is any input from some special files
|
|
|
+(such as a terminal device).
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+For the last two cases, @id{size}
|
|
|
+specifies the size of the buffer, in bytes.
|
|
|
+The default is an appropriate size.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{file:write (@Cdots)|
|
|
|
+
|
|
|
+Writes the value of each of its arguments to @id{file}.
|
|
|
+The arguments must be strings or numbers.
|
|
|
+
|
|
|
+In case of success, this function returns @id{file}.
|
|
|
+Otherwise it returns @nil plus a string describing the error.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{oslib| @title{Operating System Facilities}
|
|
|
+
|
|
|
+This library is implemented through table @defid{os}.
|
|
|
+
|
|
|
+
|
|
|
+@LibEntry{os.clock ()|
|
|
|
+
|
|
|
+Returns an approximation of the amount in seconds of CPU time
|
|
|
+used by the program.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.date ([format [, time]])|
|
|
|
+
|
|
|
+Returns a string or a table containing date and time,
|
|
|
+formatted according to the given string @id{format}.
|
|
|
+
|
|
|
+If the @id{time} argument is present,
|
|
|
+this is the time to be formatted
|
|
|
+(see the @Lid{os.time} function for a description of this value).
|
|
|
+Otherwise, @id{date} formats the current time.
|
|
|
+
|
|
|
+If @id{format} starts with @Char{!},
|
|
|
+then the date is formatted in Coordinated Universal Time.
|
|
|
+After this optional character,
|
|
|
+if @id{format} is the string @St{*t},
|
|
|
+then @id{date} returns a table with the following fields:
|
|
|
+@id{year}, @id{month} (1@En{}12), @id{day} (1@En{}31),
|
|
|
+@id{hour} (0@En{}23), @id{min} (0@En{}59),
|
|
|
+@id{sec} (0@En{}61, due to leap seconds),
|
|
|
+@id{wday} (weekday, 1@En{}7, Sunday @N{is 1}),
|
|
|
+@id{yday} (day of the year, 1@En{}366),
|
|
|
+and @id{isdst} (daylight saving flag, a boolean).
|
|
|
+This last field may be absent
|
|
|
+if the information is not available.
|
|
|
+
|
|
|
+If @id{format} is not @St{*t},
|
|
|
+then @id{date} returns the date as a string,
|
|
|
+formatted according to the same rules as the @ANSI{strftime}.
|
|
|
+
|
|
|
+When called without arguments,
|
|
|
+@id{date} returns a reasonable date and time representation that depends on
|
|
|
+the host system and on the current locale.
|
|
|
+(More specifically, @T{os.date()} is equivalent to @T{os.date("%c")}.)
|
|
|
+
|
|
|
+On non-POSIX systems,
|
|
|
+this function may be not @x{thread safe}
|
|
|
+because of its reliance on @CId{gmtime} and @CId{localtime}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.difftime (t2, t1)|
|
|
|
+
|
|
|
+Returns the difference, in seconds,
|
|
|
+from time @id{t1} to time @id{t2}
|
|
|
+(where the times are values returned by @Lid{os.time}).
|
|
|
+In @x{POSIX}, @x{Windows}, and some other systems,
|
|
|
+this value is exactly @id{t2}@M{-}@id{t1}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.execute ([command])|
|
|
|
+
|
|
|
+This function is equivalent to the @ANSI{system}.
|
|
|
+It passes @id{command} to be executed by an operating system shell.
|
|
|
+Its first result is @true
|
|
|
+if the command terminated successfully,
|
|
|
+or @nil otherwise.
|
|
|
+After this first result
|
|
|
+the function returns a string plus a number,
|
|
|
+as follows:
|
|
|
+@description{
|
|
|
+
|
|
|
+@item{@St{exit}|
|
|
|
+the command terminated normally;
|
|
|
+the following number is the exit status of the command.
|
|
|
+}
|
|
|
+
|
|
|
+@item{@St{signal}|
|
|
|
+the command was terminated by a signal;
|
|
|
+the following number is the signal that terminated the command.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+When called without a @id{command},
|
|
|
+@id{os.execute} returns a boolean that is true if a shell is available.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.exit ([code [, close]])|
|
|
|
+
|
|
|
+Calls the @ANSI{exit} to terminate the host program.
|
|
|
+If @id{code} is @Rw{true},
|
|
|
+the returned status is @idx{EXIT_SUCCESS};
|
|
|
+if @id{code} is @Rw{false},
|
|
|
+the returned status is @idx{EXIT_FAILURE};
|
|
|
+if @id{code} is a number,
|
|
|
+the returned status is this number.
|
|
|
+The default value for @id{code} is @Rw{true}.
|
|
|
+
|
|
|
+If the optional second argument @id{close} is true,
|
|
|
+closes the Lua state before exiting.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.getenv (varname)|
|
|
|
+
|
|
|
+Returns the value of the process environment variable @id{varname},
|
|
|
+or @nil if the variable is not defined.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.remove (filename)|
|
|
|
+
|
|
|
+Deletes the file (or empty directory, on @x{POSIX} systems)
|
|
|
+with the given name.
|
|
|
+If this function fails, it returns @nil,
|
|
|
+plus a string describing the error and the error code.
|
|
|
+Otherwise, it returns true.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.rename (oldname, newname)|
|
|
|
+
|
|
|
+Renames the file or directory named @id{oldname} to @id{newname}.
|
|
|
+If this function fails, it returns @nil,
|
|
|
+plus a string describing the error and the error code.
|
|
|
+Otherwise, it returns true.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.setlocale (locale [, category])|
|
|
|
+
|
|
|
+Sets the current locale of the program.
|
|
|
+@id{locale} is a system-dependent string specifying a locale;
|
|
|
+@id{category} is an optional string describing which category to change:
|
|
|
+@T{"all"}, @T{"collate"}, @T{"ctype"},
|
|
|
+@T{"monetary"}, @T{"numeric"}, or @T{"time"};
|
|
|
+the default category is @T{"all"}.
|
|
|
+The function returns the name of the new locale,
|
|
|
+or @nil if the request cannot be honored.
|
|
|
+
|
|
|
+If @id{locale} is the empty string,
|
|
|
+the current locale is set to an implementation-defined native locale.
|
|
|
+If @id{locale} is the string @St{C},
|
|
|
+the current locale is set to the standard C locale.
|
|
|
+
|
|
|
+When called with @nil as the first argument,
|
|
|
+this function only returns the name of the current locale
|
|
|
+for the given category.
|
|
|
+
|
|
|
+This function may be not @x{thread safe}
|
|
|
+because of its reliance on @CId{setlocale}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.time ([table])|
|
|
|
+
|
|
|
+Returns the current time when called without arguments,
|
|
|
+or a time representing the local date and time specified by the given table.
|
|
|
+This table must have fields @id{year}, @id{month}, and @id{day},
|
|
|
+and may have fields
|
|
|
+@id{hour} (default is 12),
|
|
|
+@id{min} (default is 0),
|
|
|
+@id{sec} (default is 0),
|
|
|
+and @id{isdst} (default is @nil).
|
|
|
+Other fields are ignored.
|
|
|
+For a description of these fields, see the @Lid{os.date} function.
|
|
|
+
|
|
|
+When the function is called,
|
|
|
+the values in these fields do not need to be inside their valid ranges.
|
|
|
+For instance, if @id{sec} is -10,
|
|
|
+it means 10 seconds before the time specified by the other fields;
|
|
|
+if @id{hour} is 1000,
|
|
|
+it means 1000 hours after the time specified by the other fields.
|
|
|
+
|
|
|
+The returned value is a number, whose meaning depends on your system.
|
|
|
+In @x{POSIX}, @x{Windows}, and some other systems,
|
|
|
+this number counts the number
|
|
|
+of seconds since some given start time (the @Q{epoch}).
|
|
|
+In other systems, the meaning is not specified,
|
|
|
+and the number returned by @id{time} can be used only as an argument to
|
|
|
+@Lid{os.date} and @Lid{os.difftime}.
|
|
|
+
|
|
|
+When called with a table,
|
|
|
+@id{os.time} also normalizes all the fields
|
|
|
+documented in the @Lid{os.date} function,
|
|
|
+so that they represent the same time as before the call
|
|
|
+but with values inside their valid ranges.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{os.tmpname ()|
|
|
|
+
|
|
|
+Returns a string with a file name that can
|
|
|
+be used for a temporary file.
|
|
|
+The file must be explicitly opened before its use
|
|
|
+and explicitly removed when no longer needed.
|
|
|
+
|
|
|
+In @x{POSIX} systems,
|
|
|
+this function also creates a file with that name,
|
|
|
+to avoid security risks.
|
|
|
+(Someone else might create the file with wrong permissions
|
|
|
+in the time between getting the name and creating the file.)
|
|
|
+You still have to open the file to use it
|
|
|
+and to remove it (even if you do not use it).
|
|
|
+
|
|
|
+When possible,
|
|
|
+you may prefer to use @Lid{io.tmpfile},
|
|
|
+which automatically removes the file when the program ends.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{debuglib| @title{The Debug Library}
|
|
|
+
|
|
|
+This library provides
|
|
|
+the functionality of the @link{debugI|debug interface} to Lua programs.
|
|
|
+You should exert care when using this library.
|
|
|
+Several of its functions
|
|
|
+violate basic assumptions about Lua code
|
|
|
+(e.g., that variables local to a function
|
|
|
+cannot be accessed from outside;
|
|
|
+that userdata metatables cannot be changed by Lua code;
|
|
|
+that Lua programs do not crash)
|
|
|
+and therefore can compromise otherwise secure code.
|
|
|
+Moreover, some functions in this library may be slow.
|
|
|
+
|
|
|
+All functions in this library are provided
|
|
|
+inside the @defid{debug} table.
|
|
|
+All functions that operate over a thread
|
|
|
+have an optional first argument which is the
|
|
|
+thread to operate over.
|
|
|
+The default is always the current thread.
|
|
|
+
|
|
|
+
|
|
|
+@LibEntry{debug.debug ()|
|
|
|
+
|
|
|
+Enters an interactive mode with the user,
|
|
|
+running each string that the user enters.
|
|
|
+Using simple commands and other debug facilities,
|
|
|
+the user can inspect global and local variables,
|
|
|
+change their values, evaluate expressions, and so on.
|
|
|
+A line containing only the word @id{cont} finishes this function,
|
|
|
+so that the caller continues its execution.
|
|
|
+
|
|
|
+Note that commands for @id{debug.debug} are not lexically nested
|
|
|
+within any function and so have no direct access to local variables.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.gethook ([thread])|
|
|
|
+
|
|
|
+Returns the current hook settings of the thread, as three values:
|
|
|
+the current hook function, the current hook mask,
|
|
|
+and the current hook count
|
|
|
+(as set by the @Lid{debug.sethook} function).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.getinfo ([thread,] f [, what])|
|
|
|
+
|
|
|
+Returns a table with information about a function.
|
|
|
+You can give the function directly
|
|
|
+or you can give a number as the value of @id{f},
|
|
|
+which means the function running at level @id{f} of the call stack
|
|
|
+of the given thread:
|
|
|
+@N{level 0} is the current function (@id{getinfo} itself);
|
|
|
+@N{level 1} is the function that called @id{getinfo}
|
|
|
+(except for tail calls, which do not count on the stack);
|
|
|
+and so on.
|
|
|
+If @id{f} is a number larger than the number of active functions,
|
|
|
+then @id{getinfo} returns @nil.
|
|
|
+
|
|
|
+The returned table can contain all the fields returned by @Lid{lua_getinfo},
|
|
|
+with the string @id{what} describing which fields to fill in.
|
|
|
+The default for @id{what} is to get all information available,
|
|
|
+except the table of valid lines.
|
|
|
+If present,
|
|
|
+the option @Char{f}
|
|
|
+adds a field named @id{func} with the function itself.
|
|
|
+If present,
|
|
|
+the option @Char{L}
|
|
|
+adds a field named @id{activelines} with the table of
|
|
|
+valid lines.
|
|
|
+
|
|
|
+For instance, the expression @T{debug.getinfo(1,"n").name} returns
|
|
|
+a name for the current function,
|
|
|
+if a reasonable name can be found,
|
|
|
+and the expression @T{debug.getinfo(print)}
|
|
|
+returns a table with all available information
|
|
|
+about the @Lid{print} function.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.getlocal ([thread,] f, local)|
|
|
|
+
|
|
|
+This function returns the name and the value of the local variable
|
|
|
+with index @id{local} of the function at level @id{f} of the stack.
|
|
|
+This function accesses not only explicit local variables,
|
|
|
+but also parameters, temporaries, etc.
|
|
|
+
|
|
|
+The first parameter or local variable has @N{index 1}, and so on,
|
|
|
+following the order that they are declared in the code,
|
|
|
+counting only the variables that are active
|
|
|
+in the current scope of the function.
|
|
|
+Negative indices refer to vararg parameters;
|
|
|
+@num{-1} is the first vararg parameter.
|
|
|
+The function returns @nil if there is no variable with the given index,
|
|
|
+and raises an error when called with a level out of range.
|
|
|
+(You can call @Lid{debug.getinfo} to check whether the level is valid.)
|
|
|
+
|
|
|
+Variable names starting with @Char{(} (open parenthesis) @C{)}
|
|
|
+represent variables with no known names
|
|
|
+(internal variables such as loop control variables,
|
|
|
+and variables from chunks saved without debug information).
|
|
|
+
|
|
|
+The parameter @id{f} may also be a function.
|
|
|
+In that case, @id{getlocal} returns only the name of function parameters.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.getmetatable (value)|
|
|
|
+
|
|
|
+Returns the metatable of the given @id{value}
|
|
|
+or @nil if it does not have a metatable.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.getregistry ()|
|
|
|
+
|
|
|
+Returns the registry table @see{registry}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.getupvalue (f, up)|
|
|
|
+
|
|
|
+This function returns the name and the value of the upvalue
|
|
|
+with index @id{up} of the function @id{f}.
|
|
|
+The function returns @nil if there is no upvalue with the given index.
|
|
|
+
|
|
|
+Variable names starting with @Char{(} (open parenthesis) @C{)}
|
|
|
+represent variables with no known names
|
|
|
+(variables from chunks saved without debug information).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.getuservalue (u, n)|
|
|
|
+
|
|
|
+Returns the @id{n}-th user value associated
|
|
|
+to the userdata @id{u} plus a boolean,
|
|
|
+@false if the userdata does not have that value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.sethook ([thread,] hook, mask [, count])|
|
|
|
+
|
|
|
+Sets the given function as a hook.
|
|
|
+The string @id{mask} and the number @id{count} describe
|
|
|
+when the hook will be called.
|
|
|
+The string mask may have any combination of the following characters,
|
|
|
+with the given meaning:
|
|
|
+@description{
|
|
|
+@item{@Char{c}| the hook is called every time Lua calls a function;}
|
|
|
+@item{@Char{r}| the hook is called every time Lua returns from a function;}
|
|
|
+@item{@Char{l}| the hook is called every time Lua enters a new line of code.}
|
|
|
+}
|
|
|
+Moreover,
|
|
|
+with a @id{count} different from zero,
|
|
|
+the hook is called also after every @id{count} instructions.
|
|
|
+
|
|
|
+When called without arguments,
|
|
|
+@Lid{debug.sethook} turns off the hook.
|
|
|
+
|
|
|
+When the hook is called, its first parameter is a string
|
|
|
+describing the event that has triggered its call:
|
|
|
+@T{"call"} (or @T{"tail call"}),
|
|
|
+@T{"return"},
|
|
|
+@T{"line"}, and @T{"count"}.
|
|
|
+For line events,
|
|
|
+the hook also gets the new line number as its second parameter.
|
|
|
+Inside a hook,
|
|
|
+you can call @id{getinfo} with @N{level 2} to get more information about
|
|
|
+the running function
|
|
|
+(@N{level 0} is the @id{getinfo} function,
|
|
|
+and @N{level 1} is the hook function).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.setlocal ([thread,] level, local, value)|
|
|
|
+
|
|
|
+This function assigns the value @id{value} to the local variable
|
|
|
+with index @id{local} of the function at level @id{level} of the stack.
|
|
|
+The function returns @nil if there is no local
|
|
|
+variable with the given index,
|
|
|
+and raises an error when called with a @id{level} out of range.
|
|
|
+(You can call @id{getinfo} to check whether the level is valid.)
|
|
|
+Otherwise, it returns the name of the local variable.
|
|
|
+
|
|
|
+See @Lid{debug.getlocal} for more information about
|
|
|
+variable indices and names.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.setmetatable (value, table)|
|
|
|
+
|
|
|
+Sets the metatable for the given @id{value} to the given @id{table}
|
|
|
+(which can be @nil).
|
|
|
+Returns @id{value}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.setupvalue (f, up, value)|
|
|
|
+
|
|
|
+This function assigns the value @id{value} to the upvalue
|
|
|
+with index @id{up} of the function @id{f}.
|
|
|
+The function returns @nil if there is no upvalue
|
|
|
+with the given index.
|
|
|
+Otherwise, it returns the name of the upvalue.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.setuservalue (udata, value, n)|
|
|
|
+
|
|
|
+Sets the given @id{value} as
|
|
|
+the @id{n}-th user value associated to the given @id{udata}.
|
|
|
+@id{udata} must be a full userdata.
|
|
|
+
|
|
|
+Returns @id{udata},
|
|
|
+or @nil if the userdata does not have that value.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.traceback ([thread,] [message [, level]])|
|
|
|
+
|
|
|
+If @id{message} is present but is neither a string nor @nil,
|
|
|
+this function returns @id{message} without further processing.
|
|
|
+Otherwise,
|
|
|
+it returns a string with a traceback of the call stack.
|
|
|
+The optional @id{message} string is appended
|
|
|
+at the beginning of the traceback.
|
|
|
+An optional @id{level} number tells at which level
|
|
|
+to start the traceback
|
|
|
+(default is 1, the function calling @id{traceback}).
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.upvalueid (f, n)|
|
|
|
+
|
|
|
+Returns a unique identifier (as a light userdata)
|
|
|
+for the upvalue numbered @id{n}
|
|
|
+from the given function.
|
|
|
+
|
|
|
+These unique identifiers allow a program to check whether different
|
|
|
+closures share upvalues.
|
|
|
+Lua closures that share an upvalue
|
|
|
+(that is, that access a same external local variable)
|
|
|
+will return identical ids for those upvalue indices.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@LibEntry{debug.upvaluejoin (f1, n1, f2, n2)|
|
|
|
+
|
|
|
+Make the @id{n1}-th upvalue of the Lua closure @id{f1}
|
|
|
+refer to the @id{n2}-th upvalue of the Lua closure @id{f2}.
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@C{-------------------------------------------------------------------------}
|
|
|
+@sect1{lua-sa| @title{Lua Standalone}
|
|
|
+
|
|
|
+Although Lua has been designed as an extension language,
|
|
|
+to be embedded in a host @N{C program},
|
|
|
+it is also frequently used as a standalone language.
|
|
|
+An interpreter for Lua as a standalone language,
|
|
|
+called simply @id{lua},
|
|
|
+is provided with the standard distribution.
|
|
|
+The @x{standalone interpreter} includes
|
|
|
+all standard libraries, including the debug library.
|
|
|
+Its usage is:
|
|
|
+@verbatim{
|
|
|
+lua [options] [script [args]]
|
|
|
+}
|
|
|
+The options are:
|
|
|
+@description{
|
|
|
+@item{@T{-e @rep{stat}}| executes string @rep{stat};}
|
|
|
+@item{@T{-l @rep{mod}}| @Q{requires} @rep{mod} and assigns the
|
|
|
+ result to global @rep{mod};}
|
|
|
+@item{@T{-i}| enters interactive mode after running @rep{script};}
|
|
|
+@item{@T{-v}| prints version information;}
|
|
|
+@item{@T{-E}| ignores environment variables;}
|
|
|
+@item{@T{--}| stops handling options;}
|
|
|
+@item{@T{-}| executes @id{stdin} as a file and stops handling options.}
|
|
|
+}
|
|
|
+After handling its options, @id{lua} runs the given @emph{script}.
|
|
|
+When called without arguments,
|
|
|
+@id{lua} behaves as @T{lua -v -i}
|
|
|
+when the standard input (@id{stdin}) is a terminal,
|
|
|
+and as @T{lua -} otherwise.
|
|
|
+
|
|
|
+When called without option @T{-E},
|
|
|
+the interpreter checks for an environment variable @defid{LUA_INIT_5_4}
|
|
|
+(or @defid{LUA_INIT} if the versioned name is not defined)
|
|
|
+before running any argument.
|
|
|
+If the variable content has the format @T{@At@rep{filename}},
|
|
|
+then @id{lua} executes the file.
|
|
|
+Otherwise, @id{lua} executes the string itself.
|
|
|
+
|
|
|
+When called with option @T{-E},
|
|
|
+besides ignoring @id{LUA_INIT},
|
|
|
+Lua also ignores
|
|
|
+the values of @id{LUA_PATH} and @id{LUA_CPATH},
|
|
|
+setting the values of
|
|
|
+@Lid{package.path} and @Lid{package.cpath}
|
|
|
+with the default paths defined in @id{luaconf.h}.
|
|
|
+
|
|
|
+All options are handled in order, except @T{-i} and @T{-E}.
|
|
|
+For instance, an invocation like
|
|
|
+@verbatim{
|
|
|
+$ lua -e'a=1' -e 'print(a)' script.lua
|
|
|
+}
|
|
|
+will first set @id{a} to 1, then print the value of @id{a},
|
|
|
+and finally run the file @id{script.lua} with no arguments.
|
|
|
+(Here @T{$} is the shell prompt. Your prompt may be different.)
|
|
|
+
|
|
|
+Before running any code,
|
|
|
+@id{lua} collects all command-line arguments
|
|
|
+in a global table called @id{arg}.
|
|
|
+The script name goes to index 0,
|
|
|
+the first argument after the script name goes to index 1,
|
|
|
+and so on.
|
|
|
+Any arguments before the script name
|
|
|
+(that is, the interpreter name plus its options)
|
|
|
+go to negative indices.
|
|
|
+For instance, in the call
|
|
|
+@verbatim{
|
|
|
+$ lua -la b.lua t1 t2
|
|
|
+}
|
|
|
+the table is like this:
|
|
|
+@verbatim{
|
|
|
+arg = { [-2] = "lua", [-1] = "-la",
|
|
|
+ [0] = "b.lua",
|
|
|
+ [1] = "t1", [2] = "t2" }
|
|
|
+}
|
|
|
+If there is no script in the call,
|
|
|
+the interpreter name goes to index 0,
|
|
|
+followed by the other arguments.
|
|
|
+For instance, the call
|
|
|
+@verbatim{
|
|
|
+$ lua -e "print(arg[1])"
|
|
|
+}
|
|
|
+will print @St{-e}.
|
|
|
+If there is a script,
|
|
|
+the script is called with parameters
|
|
|
+@T{arg[1]}, @Cdots, @T{arg[#arg]}.
|
|
|
+(Like all chunks in Lua,
|
|
|
+the script is compiled as a vararg function.)
|
|
|
+
|
|
|
+In interactive mode,
|
|
|
+Lua repeatedly prompts and waits for a line.
|
|
|
+After reading a line,
|
|
|
+Lua first try to interpret the line as an expression.
|
|
|
+If it succeeds, it prints its value.
|
|
|
+Otherwise, it interprets the line as a statement.
|
|
|
+If you write an incomplete statement,
|
|
|
+the interpreter waits for its completion
|
|
|
+by issuing a different prompt.
|
|
|
+
|
|
|
+If the global variable @defid{_PROMPT} contains a string,
|
|
|
+then its value is used as the prompt.
|
|
|
+Similarly, if the global variable @defid{_PROMPT2} contains a string,
|
|
|
+its value is used as the secondary prompt
|
|
|
+(issued during incomplete statements).
|
|
|
+
|
|
|
+In case of unprotected errors in the script,
|
|
|
+the interpreter reports the error to the standard error stream.
|
|
|
+If the error object is not a string but
|
|
|
+has a metamethod @idx{__tostring},
|
|
|
+the interpreter calls this metamethod to produce the final message.
|
|
|
+Otherwise, the interpreter converts the error object to a string
|
|
|
+and adds a stack traceback to it.
|
|
|
+
|
|
|
+When finishing normally,
|
|
|
+the interpreter closes its main Lua state
|
|
|
+@seeF{lua_close}.
|
|
|
+The script can avoid this step by
|
|
|
+calling @Lid{os.exit} to terminate.
|
|
|
+
|
|
|
+To allow the use of Lua as a
|
|
|
+script interpreter in Unix systems,
|
|
|
+the standalone interpreter skips
|
|
|
+the first line of a chunk if it starts with @T{#}.
|
|
|
+Therefore, Lua scripts can be made into executable programs
|
|
|
+by using @T{chmod +x} and @N{the @T{#!}} form,
|
|
|
+as in
|
|
|
+@verbatim{
|
|
|
+#!/usr/local/bin/lua
|
|
|
+}
|
|
|
+(Of course,
|
|
|
+the location of the Lua interpreter may be different in your machine.
|
|
|
+If @id{lua} is in your @id{PATH},
|
|
|
+then
|
|
|
+@verbatim{
|
|
|
+#!/usr/bin/env lua
|
|
|
+}
|
|
|
+is a more portable solution.)
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@sect1{incompat| @title{Incompatibilities with the Previous Version}
|
|
|
+
|
|
|
+Here we list the incompatibilities that you may find when moving a program
|
|
|
+from @N{Lua 5.3} to @N{Lua 5.4}.
|
|
|
+You can avoid some incompatibilities by compiling Lua with
|
|
|
+appropriate options (see file @id{luaconf.h}).
|
|
|
+However,
|
|
|
+all these compatibility options will be removed in the future.
|
|
|
+
|
|
|
+Lua versions can always change the C API in ways that
|
|
|
+do not imply source-code changes in a program,
|
|
|
+such as the numeric values for constants
|
|
|
+or the implementation of functions as macros.
|
|
|
+Therefore,
|
|
|
+you should not assume that binaries are compatible between
|
|
|
+different Lua versions.
|
|
|
+Always recompile clients of the Lua API when
|
|
|
+using a new version.
|
|
|
+
|
|
|
+Similarly, Lua versions can always change the internal representation
|
|
|
+of precompiled chunks;
|
|
|
+precompiled chunks are not compatible between different Lua versions.
|
|
|
+
|
|
|
+The standard paths in the official distribution may
|
|
|
+change between versions.
|
|
|
+
|
|
|
+@sect2{@title{Changes in the Language}
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{
|
|
|
+The coercion of strings to numbers in
|
|
|
+arithmetic and bitwise operations
|
|
|
+has been removed from the core language.
|
|
|
+The string library does a similar job
|
|
|
+for arithmetic (but not for bitwise) operations
|
|
|
+using the string metamethods.
|
|
|
+However, unlike in previous versions,
|
|
|
+the new implementation preserves the implicit type of the numeral
|
|
|
+in the string.
|
|
|
+For instance, the result of @T{"1" + "2"} now is an integer,
|
|
|
+not a float.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{@title{Changes in the Libraries}
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{
|
|
|
+The pseudo-random number generator used by the function @Lid{math.random}
|
|
|
+now starts with a somewhat random seed.
|
|
|
+Moreover, it uses a different algorithm.
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@sect2{@title{Changes in the API}
|
|
|
+
|
|
|
+@itemize{
|
|
|
+
|
|
|
+@item{
|
|
|
+Full userdata now has an arbitrary number of associated user values.
|
|
|
+Therefore, the functions @id{lua_newuserdata},
|
|
|
+@id{lua_setuservalue}, and @id{lua_getuservalue} were
|
|
|
+replaced by @Lid{lua_newuserdatauv},
|
|
|
+@Lid{lua_setiuservalue}, and @Lid{lua_getiuservalue},
|
|
|
+which have an extra argument.
|
|
|
+
|
|
|
+(For compatibility, the old names still work as macros assuming
|
|
|
+one single user value.)
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+The function @Lid{lua_resume} has an extra parameter.
|
|
|
+This out parameter returns the number of values on
|
|
|
+the top of the stack that were yielded or returned by the coroutine.
|
|
|
+(In older versions,
|
|
|
+those values were the entire stack.)
|
|
|
+}
|
|
|
+
|
|
|
+@item{
|
|
|
+The function @Lid{lua_version} returns the version number,
|
|
|
+instead of an address of the version number.
|
|
|
+(The Lua core should work correctly with libraries using their
|
|
|
+own static copies of the same core,
|
|
|
+so there is no need to check whether they are using the same
|
|
|
+address space.)
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+
|
|
|
+@C{[===============================================================}
|
|
|
+
|
|
|
+@sect1{BNF| @title{The Complete Syntax of Lua}
|
|
|
+
|
|
|
+Here is the complete syntax of Lua in extended BNF.
|
|
|
+As usual in extended BNF,
|
|
|
+@bnfNter{{A}} means 0 or more @bnfNter{A}s,
|
|
|
+and @bnfNter{[A]} means an optional @bnfNter{A}.
|
|
|
+(For operator precedences, see @See{prec};
|
|
|
+for a description of the terminals
|
|
|
+@bnfNter{Name}, @bnfNter{Numeral},
|
|
|
+and @bnfNter{LiteralString}, see @See{lexical}.)
|
|
|
+@index{grammar}
|
|
|
+
|
|
|
+@Produc{
|
|
|
+
|
|
|
+@producname{chunk}@producbody{block}
|
|
|
+
|
|
|
+@producname{block}@producbody{@bnfrep{stat} @bnfopt{retstat}}
|
|
|
+
|
|
|
+@producname{stat}@producbody{
|
|
|
+ @bnfter{;}
|
|
|
+@OrNL varlist @bnfter{=} explist
|
|
|
+@OrNL functioncall
|
|
|
+@OrNL label
|
|
|
+@OrNL @Rw{break}
|
|
|
+@OrNL @Rw{goto} Name
|
|
|
+@OrNL @Rw{do} block @Rw{end}
|
|
|
+@OrNL @Rw{while} exp @Rw{do} block @Rw{end}
|
|
|
+@OrNL @Rw{repeat} block @Rw{until} exp
|
|
|
+@OrNL @Rw{if} exp @Rw{then} block
|
|
|
+ @bnfrep{@Rw{elseif} exp @Rw{then} block}
|
|
|
+ @bnfopt{@Rw{else} block} @Rw{end}
|
|
|
+@OrNL @Rw{for} @bnfNter{Name} @bnfter{=} exp @bnfter{,} exp @bnfopt{@bnfter{,} exp}
|
|
|
+ @Rw{do} block @Rw{end}
|
|
|
+@OrNL @Rw{for} namelist @Rw{in} explist @Rw{do} block @Rw{end}
|
|
|
+@OrNL @Rw{function} funcname funcbody
|
|
|
+@OrNL @Rw{local} @Rw{function} @bnfNter{Name} funcbody
|
|
|
+@OrNL @Rw{local} namelist @bnfopt{@bnfter{=} explist}
|
|
|
+}
|
|
|
+
|
|
|
+@producname{retstat}@producbody{@Rw{return}
|
|
|
+ @bnfopt{explist} @bnfopt{@bnfter{;}}}
|
|
|
+
|
|
|
+@producname{label}@producbody{@bnfter{::} Name @bnfter{::}}
|
|
|
+
|
|
|
+@producname{funcname}@producbody{@bnfNter{Name} @bnfrep{@bnfter{.} @bnfNter{Name}}
|
|
|
+ @bnfopt{@bnfter{:} @bnfNter{Name}}}
|
|
|
+
|
|
|
+@producname{varlist}@producbody{var @bnfrep{@bnfter{,} var}}
|
|
|
+
|
|
|
+@producname{var}@producbody{
|
|
|
+ @bnfNter{Name}
|
|
|
+@Or prefixexp @bnfter{[} exp @bnfter{]}
|
|
|
+@Or prefixexp @bnfter{.} @bnfNter{Name}
|
|
|
+}
|
|
|
+
|
|
|
+@producname{namelist}@producbody{@bnfNter{Name} @bnfrep{@bnfter{,} @bnfNter{Name}}}
|
|
|
+
|
|
|
+
|
|
|
+@producname{explist}@producbody{exp @bnfrep{@bnfter{,} exp}}
|
|
|
+
|
|
|
+@producname{exp}@producbody{
|
|
|
+ @Rw{nil}
|
|
|
+@Or @Rw{false}
|
|
|
+@Or @Rw{true}
|
|
|
+@Or @bnfNter{Numeral}
|
|
|
+@Or @bnfNter{LiteralString}
|
|
|
+@Or @bnfter{...}
|
|
|
+@Or functiondef
|
|
|
+@OrNL prefixexp
|
|
|
+@Or tableconstructor
|
|
|
+@Or exp binop exp
|
|
|
+@Or unop exp
|
|
|
+}
|
|
|
+
|
|
|
+@producname{prefixexp}@producbody{var @Or functioncall @Or @bnfter{(} exp @bnfter{)}}
|
|
|
+
|
|
|
+@producname{functioncall}@producbody{
|
|
|
+ prefixexp args
|
|
|
+@Or prefixexp @bnfter{:} @bnfNter{Name} args
|
|
|
+}
|
|
|
+
|
|
|
+@producname{args}@producbody{
|
|
|
+ @bnfter{(} @bnfopt{explist} @bnfter{)}
|
|
|
+@Or tableconstructor
|
|
|
+@Or @bnfNter{LiteralString}
|
|
|
+}
|
|
|
+
|
|
|
+@producname{functiondef}@producbody{@Rw{function} funcbody}
|
|
|
+
|
|
|
+@producname{funcbody}@producbody{@bnfter{(} @bnfopt{parlist} @bnfter{)} block @Rw{end}}
|
|
|
+
|
|
|
+@producname{parlist}@producbody{namelist @bnfopt{@bnfter{,} @bnfter{...}}
|
|
|
+ @Or @bnfter{...}}
|
|
|
+
|
|
|
+@producname{tableconstructor}@producbody{@bnfter{@Open} @bnfopt{fieldlist} @bnfter{@Close}}
|
|
|
+
|
|
|
+@producname{fieldlist}@producbody{field @bnfrep{fieldsep field} @bnfopt{fieldsep}}
|
|
|
+
|
|
|
+@producname{field}@producbody{@bnfter{[} exp @bnfter{]} @bnfter{=} exp @Or @bnfNter{Name} @bnfter{=} exp @Or exp}
|
|
|
+
|
|
|
+@producname{fieldsep}@producbody{@bnfter{,} @Or @bnfter{;}}
|
|
|
+
|
|
|
+@producname{binop}@producbody{
|
|
|
+ @bnfter{+} @Or @bnfter{-} @Or @bnfter{*} @Or @bnfter{/} @Or @bnfter{//}
|
|
|
+ @Or @bnfter{^} @Or @bnfter{%}
|
|
|
+ @OrNL
|
|
|
+ @bnfter{&} @Or @bnfter{~} @Or @bnfter{|} @Or @bnfter{>>} @Or @bnfter{<<}
|
|
|
+ @Or @bnfter{..}
|
|
|
+ @OrNL
|
|
|
+ @bnfter{<} @Or @bnfter{<=} @Or @bnfter{>} @Or @bnfter{>=}
|
|
|
+ @Or @bnfter{==} @Or @bnfter{~=}
|
|
|
+ @OrNL
|
|
|
+ @Rw{and} @Or @Rw{or}}
|
|
|
+
|
|
|
+@producname{unop}@producbody{@bnfter{-} @Or @Rw{not} @Or @bnfter{#} @Or
|
|
|
+ @bnfter{~}}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+}
|
|
|
+
|
|
|
+@C{]===============================================================}
|
|
|
+
|
|
|
+}
|
|
|
+@C{)]-------------------------------------------------------------------------}
|
Roberto Ierusalimschy