c
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gravity-lang
mirror of https://github.com/marcobambini/gravity.git


			
				
					
						
						
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    <title>Gravity: Syntax</title>
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				<h4>INTRODUCTION</h4>
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					<li><a href="index.html"><span>Introduction</span></a></li>
					<li><a href="getting-started.html"><span>Getting Started</span></a></li>
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				<h4>LANGUAGE GUIDE</h4>
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					<li><a href="syntax.html" class="active"><span>Syntax</span></a></li>
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         	<h1 class="section-header">Syntax</h1><hr>
			
			<p class="section-content">
			<strong>Gravity</strong> syntax is designed to be familiar to people coming from C-like languages like Javascript, Swift, C++, C# and many more. We started working on this new language a year before Apple announced Swift and we were happily surprised to discovered how similar both syntax appear. Semicolon separator <strong>;</strong> is optional.
			<br><br>
			How a Gravity program looks like:</p>
			<pre><code class="swift">
	class Rectangle {
		// instance variables
		var width;
		var height;
				
		// instance method
		func area() {
			return width*height;
		}
				
		// constructor
		func init(w, h) {
			width = w;
			height = h;
		}
	}
			
	func main() {
		// initialize a new Rectangle object
		var r = Rectangle(20, 10);
				
		// return value is 20*10 = 200
		return r.area();
	}
			</code></pre>
			
			<!-- COMMENTS -->
			<h4 class="section-h4">Comments</h4>
			<p>Gravity supports both line comments:</p>
			<pre><code class="swift">
	// This is a line comment
			</code></pre>
			<p>and block comments:</p>
			<pre><code class="swift">
	/*
		This
		is
		a
		multi-line
		comment
	*/</code></pre>
			
			<!-- RESERVED KEYWORDS -->
			<h4 class="section-h4">Reserved Keywords</h4>
			<p>Like many other programming languages Gravity has some reserved keywords that assumes a very specific meaning in the context of the source code:</p>
			<pre><code class="swift">
	if in or isa for var and not func else true enum case null
	file lazy super false break while class const event _func
	_args struct repeat switch return public static extern
	import module default private continue internal undefined
			</code></pre>
			
			<!-- IDENTIFIERS -->
			<h4 class="section-h4">Identifiers</h4>
			<p>Identifiers represent a naming rule used to identifies objects inside your source code.
			Gravity is a case-sensitive language. Identifiers start with a letter or underscore and may contain letters, digits, and underscores (function identifiers can be any of the <a href="operators.html">built-in operators</a> in order to override a default behaviour):</p>
			<pre><code class="swift">
	a
	_thisIsValid
	Hello_World
	foo123
	BYE_BYE
			</code></pre>
			
			<!-- BLOCKS -->
			<h4 class="section-h4">Blocks and Scope</h4>
			<p>Every named identifier introduced in some portion of the source code is introduced in a scope. The scope is the largest part of the source code in which that identifier is valid. The names declared by a declaration are introduced into a specific scope based on the context of the declaration. For instance, local variable declarations introduce the name into the block scope, whereas class member variable declarations introduce the name into class scope.<br><br>There are three scopes defined: <strong>block scope</strong>, <strong>class scope</strong> and <strong>file scope</strong>. Names declared at block become visible immediately after its completed declarator.  This means you cannot refer to a name within block until after it has been fully declared. Names declared at file and class scope become visible immediately upon executing the starting statement of the script. This means you can refer to a name within file or class scope before it has been fully declared.<br><br>These are all valid scopes:</p>
			<pre><code class="swift">
	// file scope can refer to a name
	// before it has been fully declared
	func f1() {
	    return f2();
	}
	func f2() {
	    return 42;
	}
			
	// block scope can be nested and
	// can hide other local variables
	func f3() {
	    var a = 10;
	    if (a > 0) {
		  var a = 20;
	    }
	// 10 is returned here
	return a;
	}
			</code></pre>
			
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