package main

import "core:fmt"
import "core:mem"
import "core:os"
import "core:thread"
import "core:time"
import "core:reflect"
import "core:runtime"
import "core:intrinsics"
import "core:math/big"

/*
	The Odin programming language is fast, concise, readable, pragmatic and open sourced.
	It is designed with the intent of replacing C with the following goals:
	 * simplicity
	 * high performance
	 * built for modern systems
	 * joy of programming

	# Installing Odin
	Getting Started - https://odin-lang.org/docs/install/
		Instructions for downloading and install the Odin compiler and libraries.

	# Learning Odin
	Overview of Odin - https://odin-lang.org/docs/overview/
		An overview of the Odin programming language.
	Frequently Asked Questions (FAQ) - https://odin-lang.org/docs/faq/
		Answers to common questions about Odin.
*/

the_basics :: proc() {
	fmt.println("\n# the basics")

	{ // The Basics
		fmt.println("Hellope")

		// Lexical elements and literals
		// A comment

		my_integer_variable: int // A comment for documentaton

		// Multi-line comments begin with /* and end with */. Multi-line comments can
		// also be nested (unlike in C):
		/*
			You can have any text or code here and
			have it be commented.
			/*
				NOTE: comments can be nested!
			*/
		*/

		// String literals are enclosed in double quotes and character literals in single quotes.
		// Special characters are escaped with a backslash \

		some_string := "This is a string"
		_ = 'A' // unicode codepoint literal
		_ = '\n'
		_ = "C:\\Windows\\notepad.exe"
		// Raw string literals are enclosed with single back ticks
		_ = `C:\Windows\notepad.exe`

		// The length of a string in bytes can be found using the built-in `len` procedure:
		_ = len("Foo")
		_ = len(some_string)


		// Numbers

		// Numerical literals are written similar to most other programming languages.
		// A useful feature in Odin is that underscores are allowed for better
		// readability: 1_000_000_000 (one billion). A number that contains a dot is a
		// floating point literal: 1.0e9 (one billion). If a number literal is suffixed
		// with i, is an imaginary number literal: 2i (2 multiply the square root of -1).

		// Binary literals are prefixed with 0b, octal literals with 0o, and hexadecimal
		// literals 0x. A leading zero does not produce an octal constant (unlike C).

		// In Odin, if a numeric constant can be represented by a type without
		// precision loss, it will automatically convert to that type.

		x: int = 1.0 // A float literal but it can be represented by an integer without precision loss
		// Constant literals are “untyped” which means that they can implicitly convert to a type.

		y: int // `y` is typed of type `int`
		y = 1  // `1` is an untyped integer literal which can implicitly convert to `int`

		z: f64 // `z` is typed of type `f64` (64-bit floating point number)
		z = 1  // `1` is an untyped integer literal which can be implicitly converted to `f64`
				// No need for any suffixes or decimal places like in other languages
				// CONSTANTS JUST WORK!!!


		// Assignment statements
		h: int = 123 // declares a new variable `h` with type `int` and assigns a value to it
		h = 637 // assigns a new value to `h`

		// `=` is the assignment operator

		// You can assign multiple variables with it:
		a, b := 1, "hello" // declares `a` and `b` and infers the types from the assignments
		b, a = "byte", 0

		// Note: `:=` is two tokens, `:` and `=`. The following are equivalent,
		/*
			i: int = 123
			i:     = 123
			i := 123
		*/

		// Constant declarations
		// Constants are entities (symbols) which have an assigned value.
		// The constant’s value cannot be changed.
		// The constant’s value must be able to be evaluated at compile time:
		X :: "what" // constant `X` has the untyped string value "what"

		// Constants can be explicitly typed like a variable declaration:
		Y : int : 123
		Z :: Y + 7 // constant computations are possible

		_ = my_integer_variable
		_ = x
	}
}

control_flow :: proc() {
	fmt.println("\n# control flow")
	{ // Control flow
		// For loop
		// Odin has only one loop statement, the `for` loop

		// Basic for loop
		for i := 0; i < 10; i += 1 {
			fmt.println(i)
		}

		// NOTE: Unlike other languages like C, there are no parentheses `( )` surrounding the three components.
		// Braces `{ }` or a `do` are always required
		for i := 0; i < 10; i += 1 { }
		// for i := 0; i < 10; i += 1 do fmt.print()

		// The initial and post statements are optional
		i := 0
		for ; i < 10; {
			i += 1
		}

		// These semicolons can be dropped. This `for` loop is equivalent to C's `while` loop
		i = 0
		for i < 10 {
			i += 1
		}

		// If the condition is omitted, an infinite loop is produced:
		for {
			break
		}

		// Range-based for loop
		// The basic for loop
		for j := 0; j < 10; j += 1 {
			fmt.println(j)
		}
		// can also be written
		for j in 0..<10 {
			fmt.println(j)
		}
		for j in 0..=9 {
			fmt.println(j)
		}

		// Certain built-in types can be iterated over
		some_string := "Hello, 世界"
		for character in some_string { // Strings are assumed to be UTF-8
			fmt.println(character)
		}

		some_array := [3]int{1, 4, 9}
		for value in some_array {
			fmt.println(value)
		}

		some_slice := []int{1, 4, 9}
		for value in some_slice {
			fmt.println(value)
		}

		some_dynamic_array := [dynamic]int{1, 4, 9}
		defer delete(some_dynamic_array)
		for value in some_dynamic_array {
			fmt.println(value)
		}


		some_map := map[string]int{"A" = 1, "C" = 9, "B" = 4}
		defer delete(some_map)
		for key in some_map {
			fmt.println(key)
		}

		// Alternatively a second index value can be added
		for character, index in some_string {
			fmt.println(index, character)
		}
		for value, index in some_array {
			fmt.println(index, value)
		}
		for value, index in some_slice {
			fmt.println(index, value)
		}
		for value, index in some_dynamic_array {
			fmt.println(index, value)
		}
		for key, value in some_map {
			fmt.println(key, value)
		}

		// The iterated values are copies and cannot be written to.
		// The following idiom is useful for iterating over a container in a by-reference manner:
		for _, idx in some_slice {
			some_slice[idx] = (idx+1)*(idx+1)
		}


		// If statements
		x := 123
		if x >= 0 {
			fmt.println("x is positive")
		}

		if y := -34; y < 0 {
			fmt.println("y is negative")
		}

		if y := 123; y < 0 {
			fmt.println("y is negative")
		} else if y == 0 {
			fmt.println("y is zero")
		} else {
			fmt.println("y is positive")
		}

		// Switch statement
		// A switch statement is another way to write a sequence of if-else statements.
		// In Odin, the default case is denoted as a case without any expression.

		switch arch := ODIN_ARCH; arch {
		case "386":
			fmt.println("32-bit")
		case "amd64":
			fmt.println("64-bit")
		case: // default
			fmt.println("Unsupported architecture")
		}

		// Odin’s `switch` is like one in C or C++, except that Odin only runs the selected case.
		// This means that a `break` statement is not needed at the end of each case.
		// Another important difference is that the case values need not be integers nor constants.

		// To achieve a C-like fall through into the next case block, the keyword `fallthrough` can be used.
		one_angry_dwarf :: proc() -> int {
			fmt.println("one_angry_dwarf was called")
			return 1
		}

		switch j := 0; j {
		case 0:
		case one_angry_dwarf():
		}

		// A switch statement without a condition is the same as `switch true`.
		// This can be used to write a clean and long if-else chain and have the
		// ability to break if needed

		switch {
		case x < 0:
			fmt.println("x is negative")
		case x == 0:
			fmt.println("x is zero")
		case:
			fmt.println("x is positive")
		}

		// A `switch` statement can also use ranges like a range-based loop:
		switch c := 'j'; c {
		case 'A'..='Z', 'a'..='z', '0'..='9':
			fmt.println("c is alphanumeric")
		}

		switch x {
		case 0..<10:
			fmt.println("units")
		case 10..<13:
			fmt.println("pre-teens")
		case 13..<20:
			fmt.println("teens")
		case 20..<30:
			fmt.println("twenties")
		}
	}

	{ // Defer statement
		// A defer statement defers the execution of a statement until the end of
		// the scope it is in.

		// The following will print 4 then 234:
		{
			x := 123
			defer fmt.println(x)
			{
				defer x = 4
				x = 2
			}
			fmt.println(x)

			x = 234
		}

		// You can defer an entire block too:
		{
			bar :: proc() {}

			defer {
				fmt.println("1")
				fmt.println("2")
			}

			cond := false
			defer if cond {
				bar()
			}
		}

		// Defer statements are executed in the reverse order that they were declared:
		{
			defer fmt.println("1")
			defer fmt.println("2")
			defer fmt.println("3")
		}
		// Will print 3, 2, and then 1.

		if false {
			f, err := os.open("my_file.txt")
			if err != 0 {
				// handle error
			}
			defer os.close(f)
			// rest of code
		}
	}

	{ // When statement
		/*
			The when statement is almost identical to the if statement but with some differences:

			* Each condition must be a constant expression as a when
			  statement is evaluated at compile time.
			* The statements within a branch do not create a new scope
			* The compiler checks the semantics and code only for statements
			  that belong to the first condition that is true
			* An initial statement is not allowed in a when statement
			* when statements are allowed at file scope
		*/

		// Example
		when ODIN_ARCH == "386" {
			fmt.println("32 bit")
		} else when ODIN_ARCH == "amd64" {
			fmt.println("64 bit")
		} else {
			fmt.println("Unsupported architecture")
		}
		// The when statement is very useful for writing platform specific code.
		// This is akin to the #if construct in C’s preprocessor however, in Odin,
		// it is type checked.
	}

	{ // Branch statements
		cond, cond1, cond2 := false, false, false
		one_step :: proc() { fmt.println("one_step") }
		beyond :: proc() { fmt.println("beyond") }

		// Break statement
		for cond {
			switch {
			case:
				if cond {
					break // break out of the `switch` statement
				}
			}

			break // break out of the `for` statement
		}

		loop: for cond1 {
			for cond2 {
				break loop // leaves both loops
			}
		}

		// Continue statement
		for cond {
			if cond2 {
				continue
			}
			fmt.println("Hellope")
		}

		// Fallthrough statement

		// Odin’s switch is like one in C or C++, except that Odin only runs the selected
		// case. This means that a break statement is not needed at the end of each case.
		// Another important difference is that the case values need not be integers nor
		// constants.

		// fallthrough can be used to explicitly fall through into the next case block:

		switch i := 0; i {
		case 0:
			one_step()
			fallthrough
		case 1:
			beyond()
		}
	}
}


named_proc_return_parameters :: proc() {
	fmt.println("\n# named proc return parameters")

	foo0 :: proc() -> int {
		return 123
	}
	foo1 :: proc() -> (a: int) {
		a = 123
		return
	}
	foo2 :: proc() -> (a, b: int) {
		// Named return values act like variables within the scope
		a = 321
		b = 567
		return b, a
	}
	fmt.println("foo0 =", foo0()) // 123
	fmt.println("foo1 =", foo1()) // 123
	fmt.println("foo2 =", foo2()) // 567 321
}


explicit_procedure_overloading :: proc() {
	fmt.println("\n# explicit procedure overloading")

	add_ints :: proc(a, b: int) -> int {
		x := a + b
		fmt.println("add_ints", x)
		return x
	}
	add_floats :: proc(a, b: f32) -> f32 {
		x := a + b
		fmt.println("add_floats", x)
		return x
	}
	add_numbers :: proc(a: int, b: f32, c: u8) -> int {
		x := int(a) + int(b) + int(c)
		fmt.println("add_numbers", x)
		return x
	}

	add :: proc{add_ints, add_floats, add_numbers}

	add(int(1), int(2))
	add(f32(1), f32(2))
	add(int(1), f32(2), u8(3))

	add(1, 2)     // untyped ints coerce to int tighter than f32
	add(1.0, 2.0) // untyped floats coerce to f32 tighter than int
	add(1, 2, 3)  // three parameters

	// Ambiguous answers
	// add(1.0, 2)
	// add(1, 2.0)
}

struct_type :: proc() {
	fmt.println("\n# struct type")
	// A struct is a record type in Odin. It is a collection of fields.
	// Struct fields are accessed by using a dot:
	{
		Vector2 :: struct {
			x: f32,
			y: f32,
		}
		v := Vector2{1, 2}
		v.x = 4
		fmt.println(v.x)

		// Struct fields can be accessed through a struct pointer:

		v = Vector2{1, 2}
		p := &v
		p.x = 1335
		fmt.println(v)

		// We could write p^.x, however, it is to nice abstract the ability
		// to not explicitly dereference the pointer. This is very useful when
		// refactoring code to use a pointer rather than a value, and vice versa.
	}
	{
		// A struct literal can be denoted by providing the struct’s type
		// followed by {}. A struct literal must either provide all the
		// arguments or none:
		Vector3 :: struct {
			x, y, z: f32,
		}
		v: Vector3
		v = Vector3{} // Zero value
		v = Vector3{1, 4, 9}

		// You can list just a subset of the fields if you specify the
		// field by name (the order of the named fields does not matter):
		v = Vector3{z=1, y=2}
		assert(v.x == 0)
		assert(v.y == 2)
		assert(v.z == 1)
	}
	{
		// Structs can tagged with different memory layout and alignment requirements:

		a :: struct #align 4   {} // align to 4 bytes
		b :: struct #packed    {} // remove padding between fields
		c :: struct #raw_union {} // all fields share the same offset (0). This is the same as C's union
	}

}


union_type :: proc() {
	fmt.println("\n# union type")
	{
		val: union{int, bool}
		val = 137
		if i, ok := val.(int); ok {
			fmt.println(i)
		}
		val = true
		fmt.println(val)

		val = nil

		switch v in val {
		case int:  fmt.println("int",  v)
		case bool: fmt.println("bool", v)
		case:      fmt.println("nil")
		}
	}
	{
		// There is a duality between `any` and `union`
		// An `any` has a pointer to the data and allows for any type (open)
		// A `union` has as binary blob to store the data and allows only certain types (closed)
		// The following code is with `any` but has the same syntax
		val: any
		val = 137
		if i, ok := val.(int); ok {
			fmt.println(i)
		}
		val = true
		fmt.println(val)

		val = nil

		switch v in val {
		case int:  fmt.println("int",  v)
		case bool: fmt.println("bool", v)
		case:      fmt.println("nil")
		}
	}

	Vector3 :: distinct [3]f32
	Quaternion :: distinct quaternion128

	// More realistic examples
	{
		// NOTE(bill): For the above basic examples, you may not have any
		// particular use for it. However, my main use for them is not for these
		// simple cases. My main use is for hierarchical types. Many prefer
		// subtyping, embedding the base data into the derived types. Below is
		// an example of this for a basic game Entity.

		Entity :: struct {
			id:          u64,
			name:        string,
			position:    Vector3,
			orientation: Quaternion,

			derived: any,
		}

		Frog :: struct {
			using entity: Entity,
			jump_height:  f32,
		}

		Monster :: struct {
			using entity: Entity,
			is_robot:     bool,
			is_zombie:    bool,
		}

		// See `parametric_polymorphism` procedure for details
		new_entity :: proc($T: typeid) -> ^Entity {
			t := new(T)
			t.derived = t^
			return t
		}

		entity := new_entity(Monster)

		switch e in entity.derived {
		case Frog:
			fmt.println("Ribbit")
		case Monster:
			if e.is_robot  { fmt.println("Robotic") }
			if e.is_zombie { fmt.println("Grrrr!")  }
			fmt.println("I'm a monster")
		}
	}

	{
		// NOTE(bill): A union can be used to achieve something similar. Instead
		// of embedding the base data into the derived types, the derived data
		// in embedded into the base type. Below is the same example of the
		// basic game Entity but using an union.

		Entity :: struct {
			id:          u64,
			name:        string,
			position:    Vector3,
			orientation: Quaternion,

			derived: union {Frog, Monster},
		}

		Frog :: struct {
			using entity: ^Entity,
			jump_height:  f32,
		}

		Monster :: struct {
			using entity: ^Entity,
			is_robot:     bool,
			is_zombie:    bool,
		}

		// See `parametric_polymorphism` procedure for details
		new_entity :: proc($T: typeid) -> ^Entity {
			t := new(Entity)
			t.derived = T{entity = t}
			return t
		}

		entity := new_entity(Monster)

		switch e in entity.derived {
		case Frog:
			fmt.println("Ribbit")
		case Monster:
			if e.is_robot  { fmt.println("Robotic") }
			if e.is_zombie { fmt.println("Grrrr!")  }
		}

		// NOTE(bill): As you can see, the usage code has not changed, only its
		// memory layout. Both approaches have their own advantages but they can
		// be used together to achieve different results. The subtyping approach
		// can allow for a greater control of the memory layout and memory
		// allocation, e.g. storing the derivatives together. However, this is
		// also its disadvantage. You must either preallocate arrays for each
		// derivative separation (which can be easily missed) or preallocate a
		// bunch of "raw" memory; determining the maximum size of the derived
		// types would require the aid of metaprogramming. Unions solve this
		// particular problem as the data is stored with the base data.
		// Therefore, it is possible to preallocate, e.g. [100]Entity.

		// It should be noted that the union approach can have the same memory
		// layout as the any and with the same type restrictions by using a
		// pointer type for the derivatives.

		/*
			Entity :: struct {
				...
				derived: union{^Frog, ^Monster},
			}

			Frog :: struct {
				using entity: Entity,
				...
			}
			Monster :: struct {
				using entity: Entity,
				...

			}
			new_entity :: proc(T: type) -> ^Entity {
				t := new(T)
				t.derived = t
				return t
			}
		*/
	}
}

using_statement :: proc() {
	fmt.println("\n# using statement")
	// using can used to bring entities declared in a scope/namespace
	// into the current scope. This can be applied to import names, struct
	// fields, procedure fields, and struct values.

	Vector3 :: struct{x, y, z: f32}
	{
		Entity :: struct {
			position: Vector3,
			orientation: quaternion128,
		}

		// It can used like this:
		foo0 :: proc(entity: ^Entity) {
			fmt.println(entity.position.x, entity.position.y, entity.position.z)
		}

		// The entity members can be brought into the procedure scope by using it:
		foo1 :: proc(entity: ^Entity) {
			using entity
			fmt.println(position.x, position.y, position.z)
		}

		// The using can be applied to the parameter directly:
		foo2 :: proc(using entity: ^Entity) {
			fmt.println(position.x, position.y, position.z)
		}

		// It can also be applied to sub-fields:
		foo3 :: proc(entity: ^Entity) {
			using entity.position
			fmt.println(x, y, z)
		}
	}
	{
		// We can also apply the using statement to the struct fields directly,
		// making all the fields of position appear as if they on Entity itself:
		Entity :: struct {
			using position: Vector3,
			orientation: quaternion128,
		}
		foo :: proc(entity: ^Entity) {
			fmt.println(entity.x, entity.y, entity.z)
		}


		// Subtype polymorphism
		// It is possible to get subtype polymorphism, similar to inheritance-like
		// functionality in C++, but without the requirement of vtables or unknown
		// struct layout:

		Colour :: struct {r, g, b, a: u8}
		Frog :: struct {
			ribbit_volume: f32,
			using entity: Entity,
			colour: Colour,
		}

		frog: Frog
		// Both work
		foo(&frog.entity)
		foo(&frog)
		frog.x = 123

		// Note: using can be applied to arbitrarily many things, which allows
		// the ability to have multiple subtype polymorphism (but also its issues).

		// Note: using’d fields can still be referred by name.
	}
}


implicit_context_system :: proc() {
	fmt.println("\n# implicit context system")
	// In each scope, there is an implicit value named context. This
	// context variable is local to each scope and is implicitly passed
	// by pointer to any procedure call in that scope (if the procedure
	// has the Odin calling convention).

	// The main purpose of the implicit context system is for the ability
	// to intercept third-party code and libraries and modify their
	// functionality. One such case is modifying how a library allocates
	// something or logs something. In C, this was usually achieved with
	// the library defining macros which could be overridden so that the
	// user could define what he wanted. However, not many libraries
	// supported this in many languages by default which meant intercepting
	// third-party code to see what it does and to change how it does it is
	// not possible.

	c := context // copy the current scope's context

	context.user_index = 456
	{
		context.allocator = my_custom_allocator()
		context.user_index = 123
		what_a_fool_believes() // the `context` for this scope is implicitly passed to `what_a_fool_believes`
	}

	// `context` value is local to the scope it is in
	assert(context.user_index == 456)

	what_a_fool_believes :: proc() {
		c := context // this `context` is the same as the parent procedure that it was called from
		// From this example, context.user_index == 123
		// An context.allocator is assigned to the return value of `my_custom_allocator()`
		assert(context.user_index == 123)

		// The memory management procedure use the `context.allocator` by
		// default unless explicitly specified otherwise
		china_grove := new(int)
		free(china_grove)

		_ = c
	}

	my_custom_allocator :: mem.nil_allocator
	_ = c

	// By default, the context value has default values for its parameters which is
	// decided in the package runtime. What the defaults are are compiler specific.

	// To see what the implicit context value contains, please see the following
	// definition in package runtime.
}

parametric_polymorphism :: proc() {
	fmt.println("\n# parametric polymorphism")

	print_value :: proc(value: $T) {
		fmt.printf("print_value: %T %v\n", value, value)
	}

	v1: int    = 1
	v2: f32    = 2.1
	v3: f64    = 3.14
	v4: string = "message"

	print_value(v1)
	print_value(v2)
	print_value(v3)
	print_value(v4)

	fmt.println()

	add :: proc(p, q: $T) -> T {
		x: T = p + q
		return x
	}

	a := add(3, 4)
	fmt.printf("a: %T = %v\n", a, a)

	b := add(3.2, 4.3)
	fmt.printf("b: %T = %v\n", b, b)

	// This is how `new` is implemented
	alloc_type :: proc($T: typeid) -> ^T {
		t := cast(^T)alloc(size_of(T), align_of(T))
		t^ = T{} // Use default initialization value
		return t
	}

	copy_slice :: proc(dst, src: []$T) -> int {
		n := min(len(dst), len(src))
		if n > 0 {
			mem.copy(&dst[0], &src[0], n*size_of(T))
		}
		return n
	}

	double_params :: proc(a: $A, b: $B) -> A {
		return a + A(b)
	}

	fmt.println(double_params(12, 1.345))



	{ // Polymorphic Types and Type Specialization
		Table_Slot :: struct($Key, $Value: typeid) {
			occupied: bool,
			hash:     u32,
			key:      Key,
			value:    Value,
		}
		TABLE_SIZE_MIN :: 32
		Table :: struct($Key, $Value: typeid) {
			count:     int,
			allocator: mem.Allocator,
			slots:     []Table_Slot(Key, Value),
		}

		// Only allow types that are specializations of a (polymorphic) slice
		make_slice :: proc($T: typeid/[]$E, len: int) -> T {
			return make(T, len)
		}

		// Only allow types that are specializations of `Table`
		allocate :: proc(table: ^$T/Table, capacity: int) {
			c := context
			if table.allocator.procedure != nil {
				c.allocator = table.allocator
			}
			context = c

			table.slots = make_slice(type_of(table.slots), max(capacity, TABLE_SIZE_MIN))
		}

		expand :: proc(table: ^$T/Table) {
			c := context
			if table.allocator.procedure != nil {
				c.allocator = table.allocator
			}
			context = c

			old_slots := table.slots
			defer delete(old_slots)

			cap := max(2*len(table.slots), TABLE_SIZE_MIN)
			allocate(table, cap)

			for s in old_slots {
				if s.occupied {
					put(table, s.key, s.value)
				}
			}
		}

		// Polymorphic determination of a polymorphic struct
		// put :: proc(table: ^$T/Table, key: T.Key, value: T.Value) {
		put :: proc(table: ^Table($Key, $Value), key: Key, value: Value) {
			hash := get_hash(key) // Ad-hoc method which would fail in a different scope
			index := find_index(table, key, hash)
			if index < 0 {
				if f64(table.count) >= 0.75*f64(len(table.slots)) {
					expand(table)
				}
				assert(table.count <= len(table.slots))

				index = int(hash % u32(len(table.slots)))

				for table.slots[index].occupied {
					if index += 1; index >= len(table.slots) {
						index = 0
					}
				}

				table.count += 1
			}

			slot := &table.slots[index]
			slot.occupied = true
			slot.hash     = hash
			slot.key      = key
			slot.value    = value
		}


		// find :: proc(table: ^$T/Table, key: T.Key) -> (T.Value, bool) {
		find :: proc(table: ^Table($Key, $Value), key: Key) -> (Value, bool) {
			hash := get_hash(key)
			index := find_index(table, key, hash)
			if index < 0 {
				return Value{}, false
			}
			return table.slots[index].value, true
		}

		find_index :: proc(table: ^Table($Key, $Value), key: Key, hash: u32) -> int {
			if len(table.slots) <= 0 {
				return -1
			}

			index := int(hash % u32(len(table.slots)))
			for table.slots[index].occupied {
				if table.slots[index].hash == hash {
					if table.slots[index].key == key {
						return index
					}
				}

				if index += 1; index >= len(table.slots) {
					index = 0
				}
			}

			return -1
		}

		get_hash :: proc(s: string) -> u32 { // fnv32a
			h: u32 = 0x811c9dc5
			for i in 0..<len(s) {
				h = (h ~ u32(s[i])) * 0x01000193
			}
			return h
		}


		table: Table(string, int)

		for i in 0..=36 { put(&table, "Hellope", i) }
		for i in 0..=42 { put(&table, "World!",  i) }

		found, _ := find(&table, "Hellope")
		fmt.printf("`found` is %v\n", found)

		found, _ = find(&table, "World!")
		fmt.printf("`found` is %v\n", found)

		// I would not personally design a hash table like this in production
		// but this is a nice basic example
		// A better approach would either use a `u64` or equivalent for the key
		// and let the user specify the hashing function or make the user store
		// the hashing procedure with the table
	}

	{ // Parametric polymorphic union
		Error :: enum {
			Foo0,
			Foo1,
			Foo2,
			Foo3,
		}
		Para_Union :: union($T: typeid) {T, Error}
		r: Para_Union(int)
		fmt.println(typeid_of(type_of(r)))

		fmt.println(r)
		r = 123
		fmt.println(r)
		r = Error.Foo0 // r = .Foo0 is allow too, see implicit selector expressions below
		fmt.println(r)
	}

	{ // Polymorphic names
		foo :: proc($N: $I, $T: typeid) -> (res: [N]T) {
			// `N` is the constant value passed
			// `I` is the type of N
			// `T` is the type passed
			fmt.printf("Generating an array of type %v from the value %v of type %v\n",
					   typeid_of(type_of(res)), N, typeid_of(I))
			for i in 0..<N {
				res[i] = T(i*i)
			}
			return
		}

		T :: int
		array := foo(4, T)
		for v, i in array {
			assert(v == T(i*i))
		}

		// Matrix multiplication
		mul :: proc(a: [$M][$N]$T, b: [N][$P]T) -> (c: [M][P]T) {
			for i in 0..<M {
				for j in 0..<P {
					for k in 0..<N {
						c[i][j] += a[i][k] * b[k][j]
					}
				}
			}
			return
		}

		x := [2][3]f32{
			{1, 2, 3},
			{3, 2, 1},
		}
		y := [3][2]f32{
			{0, 8},
			{6, 2},
			{8, 4},
		}
		z := mul(x, y)
		assert(z == {{36, 24}, {20, 32}})
	}
}


prefix_table := [?]string{
	"White",
	"Red",
	"Green",
	"Blue",
	"Octarine",
	"Black",
}

threading_example :: proc() {
	if ODIN_OS == "darwin" {
		// TODO: Fix threads on darwin/macOS
		return
	}

	fmt.println("\n# threading_example")

	{ // Basic Threads
		fmt.println("\n## Basic Threads")
		worker_proc :: proc(t: ^thread.Thread) {
			for iteration in 1..=5 {
				fmt.printf("Thread %d is on iteration %d\n", t.user_index, iteration)
				fmt.printf("`%s`: iteration %d\n", prefix_table[t.user_index], iteration)
				time.sleep(1 * time.Millisecond)
			}
		}

		threads := make([dynamic]^thread.Thread, 0, len(prefix_table))
		defer delete(threads)

		for in prefix_table {
			if t := thread.create(worker_proc); t != nil {
				t.init_context = context
				t.user_index = len(threads)
				append(&threads, t)
				thread.start(t)
			}
		}

		for len(threads) > 0 {
			for i := 0; i < len(threads); /**/ {
				if t := threads[i]; thread.is_done(t) {
					fmt.printf("Thread %d is done\n", t.user_index)
					thread.destroy(t)

					ordered_remove(&threads, i)
				} else {
					i += 1
				}
			}
		}
	}

	{ // Thread Pool
		fmt.println("\n## Thread Pool")
		task_proc :: proc(t: ^thread.Task) {
			index := t.user_index % len(prefix_table)
			for iteration in 1..=5 {
				fmt.printf("Worker Task %d is on iteration %d\n", t.user_index, iteration)
				fmt.printf("`%s`: iteration %d\n", prefix_table[index], iteration)
				time.sleep(1 * time.Millisecond)
			}
		}

		pool: thread.Pool
		thread.pool_init(pool=&pool, thread_count=3)
		defer thread.pool_destroy(&pool)


		for i in 0..<30 {
			thread.pool_add_task(pool=&pool, procedure=task_proc, data=nil, user_index=i)
		}

		thread.pool_start(&pool)
		thread.pool_wait_and_process(&pool)
	}
}


array_programming :: proc() {
	fmt.println("\n# array programming")
	{
		a := [3]f32{1, 2, 3}
		b := [3]f32{5, 6, 7}
		c := a * b
		d := a + b
		e := 1 +  (c - d) / 2
		fmt.printf("%.1f\n", e) // [0.5, 3.0, 6.5]
	}

	{
		a := [3]f32{1, 2, 3}
		b := swizzle(a, 2, 1, 0)
		assert(b == [3]f32{3, 2, 1})

		c := swizzle(a, 0, 0)
		assert(c == [2]f32{1, 1})
		assert(c == 1)
	}

	{
		Vector3 :: distinct [3]f32
		a := Vector3{1, 2, 3}
		b := Vector3{5, 6, 7}
		c := (a * b)/2 + 1
		d := c.x + c.y + c.z
		fmt.printf("%.1f\n", d) // 22.0

		cross :: proc(a, b: Vector3) -> Vector3 {
			i := swizzle(a, 1, 2, 0) * swizzle(b, 2, 0, 1)
			j := swizzle(a, 2, 0, 1) * swizzle(b, 1, 2, 0)
			return i - j
		}

		cross_shorter :: proc(a, b: Vector3) -> Vector3 {
			i := a.yzx * b.zxy
			j := a.zxy * b.yzx
			return i - j
		}

		blah :: proc(a: Vector3) -> f32 {
			return a.x + a.y + a.z
		}

		x := cross(a, b)
		fmt.println(x)
		fmt.println(blah(x))
	}
}

map_type :: proc() {
	fmt.println("\n# map type")

	m := make(map[string]int)
	defer delete(m)

	m["Bob"] = 2
	m["Ted"] = 5
	fmt.println(m["Bob"])

	delete_key(&m, "Ted")

	// If an element of a key does not exist, the zero value of the
	// element will be returned. To check to see if an element exists
	// can be done in two ways:
	elem, ok := m["Bob"]
	exists := "Bob" in m
	_, _ = elem, ok
	_ = exists
}

implicit_selector_expression :: proc() {
	fmt.println("\n# implicit selector expression")

	Foo :: enum {A, B, C}

	f: Foo
	f = Foo.A
	f = .A

	BAR :: bit_set[Foo]{.B, .C}

	switch f {
	case .A:
		fmt.println("HITHER")
	case .B:
		fmt.println("NEVER")
	case .C:
		fmt.println("FOREVER")
	}

	my_map := make(map[Foo]int)
	defer delete(my_map)

	my_map[.A] = 123
	my_map[Foo.B] = 345

	fmt.println(my_map[.A] + my_map[Foo.B] + my_map[.C])
}


partial_switch :: proc() {
	fmt.println("\n# partial_switch")
	{ // enum
		Foo :: enum {
			A,
			B,
			C,
			D,
		}

		f := Foo.A
		switch f {
		case .A: fmt.println("A")
		case .B: fmt.println("B")
		case .C: fmt.println("C")
		case .D: fmt.println("D")
		case:    fmt.println("?")
		}

		#partial switch f {
		case .A: fmt.println("A")
		case .D: fmt.println("D")
		}
	}
	{ // union
		Foo :: union {int, bool}
		f: Foo = 123
		switch in f {
		case int:  fmt.println("int")
		case bool: fmt.println("bool")
		case:
		}

		#partial switch in f {
		case bool: fmt.println("bool")
		}
	}
}

cstring_example :: proc() {
	fmt.println("\n# cstring_example")

	W :: "Hellope"
	X :: cstring(W)
	Y :: string(X)

	w := W
	_ = w
	x: cstring = X
	y: string = Y
	z := string(x)
	fmt.println(x, y, z)
	fmt.println(len(x), len(y), len(z))
	fmt.println(len(W), len(X), len(Y))
	// IMPORTANT NOTE for cstring variables
	// len(cstring) is O(N)
	// cast(string)cstring is O(N)
}

bit_set_type :: proc() {
	fmt.println("\n# bit_set type")

	{
		Day :: enum {
			Sunday,
			Monday,
			Tuesday,
			Wednesday,
			Thursday,
			Friday,
			Saturday,
		}

		Days :: distinct bit_set[Day]
		WEEKEND :: Days{.Sunday, .Saturday}

		d: Days
		d = {.Sunday, .Monday}
		e := d + WEEKEND
		e += {.Monday}
		fmt.println(d, e)

		ok := .Saturday in e // `in` is only allowed for `map` and `bit_set` types
		fmt.println(ok)
		if .Saturday in e {
			fmt.println("Saturday in", e)
		}
		X :: .Saturday in WEEKEND // Constant evaluation
		fmt.println(X)
		fmt.println("Cardinality:", card(e))
	}
	{
		x: bit_set['A'..='Z']
		#assert(size_of(x) == size_of(u32))
		y: bit_set[0..=8; u16]
		fmt.println(typeid_of(type_of(x))) // bit_set[A..=Z]
		fmt.println(typeid_of(type_of(y))) // bit_set[0..=8; u16]

		x += {'F'}
		assert('F' in x)
		x -= {'F'}
		assert('F' not_in x)

		y += {1, 4, 2}
		assert(2 in y)
	}
	{
		Letters :: bit_set['A'..='Z']
		a := Letters{'A', 'B'}
		b := Letters{'A', 'B', 'C', 'D', 'F'}
		c := Letters{'A', 'B'}

		assert(a <= b) // 'a' is a subset of 'b'
		assert(b >= a) // 'b' is a superset of 'a'
		assert(a < b)  // 'a' is a strict subset of 'b'
		assert(b > a)  // 'b' is a strict superset of 'a'

		assert(!(a < c)) // 'a' is a not strict subset of 'c'
		assert(!(c > a)) // 'c' is a not strict superset of 'a'
	}
}

deferred_procedure_associations :: proc() {
	fmt.println("\n# deferred procedure associations")

	@(deferred_out=closure)
	open :: proc(s: string) -> bool {
		fmt.println(s)
		return true
	}

	closure :: proc(ok: bool) {
		fmt.println("Goodbye?", ok)
	}

	if open("Welcome") {
		fmt.println("Something in the middle, mate.")
	}
}

reflection :: proc() {
	fmt.println("\n# reflection")

	Foo :: struct {
		x: int    `tag1`,
		y: string `json:"y_field"`,
		z: bool, // no tag
	}

	id := typeid_of(Foo)
	names := reflect.struct_field_names(id)
	types := reflect.struct_field_types(id)
	tags  := reflect.struct_field_tags(id)

	assert(len(names) == len(types) && len(names) == len(tags))

	fmt.println("Foo :: struct {")
	for tag, i in tags {
		name, type := names[i], types[i]
		if tag != "" {
			fmt.printf("\t%s: %T `%s`,\n", name, type, tag)
		} else {
			fmt.printf("\t%s: %T,\n", name, type)
		}
	}
	fmt.println("}")


	for tag, i in tags {
		if val, ok := reflect.struct_tag_lookup(tag, "json"); ok {
			fmt.printf("json: %s -> %s\n", names[i], val)
		}
	}
}

quaternions :: proc() {
	// Not just an April Fool's Joke any more, but a fully working thing!
	fmt.println("\n# quaternions")

	{ // Quaternion operations
		q := 1 + 2i + 3j + 4k
		r := quaternion(5, 6, 7, 8)
		t := q * r
		fmt.printf("(%v) * (%v) = %v\n", q, r, t)
		v := q / r
		fmt.printf("(%v) / (%v) = %v\n", q, r, v)
		u := q + r
		fmt.printf("(%v) + (%v) = %v\n", q, r, u)
		s := q - r
		fmt.printf("(%v) - (%v) = %v\n", q, r, s)
	}
	{ // The quaternion types
		q128: quaternion128 // 4xf32
		q256: quaternion256 // 4xf64
		q128 = quaternion(1, 0, 0, 0)
		q256 = 1 // quaternion(1, 0, 0, 0)
	}
	{ // Built-in procedures
		q := 1 + 2i + 3j + 4k
		fmt.println("q =", q)
		fmt.println("real(q) =", real(q))
		fmt.println("imag(q) =", imag(q))
		fmt.println("jmag(q) =", jmag(q))
		fmt.println("kmag(q) =", kmag(q))
		fmt.println("conj(q) =", conj(q))
		fmt.println("abs(q)  =", abs(q))
	}
	{ // Conversion of a complex type to a quaternion type
		c := 1 + 2i
		q := quaternion256(c)
		fmt.println(c)
		fmt.println(q)
	}
	{ // Memory layout of Quaternions
		q := 1 + 2i + 3j + 4k
		a := transmute([4]f64)q
		fmt.println("Quaternion memory layout: xyzw/(ijkr)")
		fmt.println(q) // 1.000+2.000i+3.000j+4.000k
		fmt.println(a) // [2.000, 3.000, 4.000, 1.000]
	}
}

unroll_for_statement :: proc() {
	fmt.println("\n#'#unroll for' statements")

	// '#unroll for' works the same as if the 'inline' prefix did not
	// exist but these ranged loops are explicitly unrolled which can
	// be very very useful for certain optimizations

	fmt.println("Ranges")
	#unroll for x, i in 1..<4 {
		fmt.println(x, i)
	}

	fmt.println("Strings")
	#unroll for r, i in "Hello, 世界" {
		fmt.println(r, i)
	}

	fmt.println("Arrays")
	#unroll for elem, idx in ([4]int{1, 4, 9, 16}) {
		fmt.println(elem, idx)
	}


	Foo_Enum :: enum {
		A = 1,
		B,
		C = 6,
		D,
	}
	fmt.println("Enum types")
	#unroll for elem, idx in Foo_Enum {
		fmt.println(elem, idx)
	}
}

where_clauses :: proc() {
	fmt.println("\n#procedure 'where' clauses")

	{ // Sanity checks
		simple_sanity_check :: proc(x: [2]int)
			where len(x) > 1,
				  type_of(x) == [2]int {
			fmt.println(x)
		}
	}
	{ // Parametric polymorphism checks
		cross_2d :: proc(a, b: $T/[2]$E) -> E
			where intrinsics.type_is_numeric(E) {
			return a.x*b.y - a.y*b.x
		}
		cross_3d :: proc(a, b: $T/[3]$E) -> T
			where intrinsics.type_is_numeric(E) {
			x := a.y*b.z - a.z*b.y
			y := a.z*b.x - a.x*b.z
			z := a.x*b.y - a.y*b.z
			return T{x, y, z}
		}

		a := [2]int{1, 2}
		b := [2]int{5, -3}
		fmt.println(cross_2d(a, b))

		x := [3]f32{1, 4, 9}
		y := [3]f32{-5, 0, 3}
		fmt.println(cross_3d(x, y))

		// Failure case
		// i := [2]bool{true, false}
		// j := [2]bool{false, true}
		// fmt.println(cross_2d(i, j))

	}

	{ // Procedure groups usage
		foo :: proc(x: [$N]int) -> bool
			where N > 2 {
			fmt.println(#procedure, "was called with the parameter", x)
			return true
		}

		bar :: proc(x: [$N]int) -> bool
			where 0 < N,
				  N <= 2 {
			fmt.println(#procedure, "was called with the parameter", x)
			return false
		}

		baz :: proc{foo, bar}

		x := [3]int{1, 2, 3}
		y := [2]int{4, 9}
		ok_x := baz(x)
		ok_y := baz(y)
		assert(ok_x == true)
		assert(ok_y == false)
	}

	{ // Record types
		Foo :: struct($T: typeid, $N: int)
			where intrinsics.type_is_integer(T),
				  N > 2 {
			x: [N]T,
			y: [N-2]T,
		}

		T :: i32
		N :: 5
		f: Foo(T, N)
		#assert(size_of(f) == (N+N-2)*size_of(T))
	}
}


when ODIN_OS == "windows" {
	foreign import kernel32 "system:kernel32.lib"
}

foreign_system :: proc() {
	fmt.println("\n#foreign system")
	when ODIN_OS == "windows" {
		// It is sometimes necessarily to interface with foreign code,
		// such as a C library. In Odin, this is achieved through the
		// foreign system. You can “import” a library into the code
		// using the same semantics as a normal import declaration.

		// This foreign import declaration will create a
		// “foreign import name” which can then be used to associate
		// entities within a foreign block.

		foreign kernel32 {
			ExitProcess :: proc "stdcall" (exit_code: u32) ---
		}

		// Foreign procedure declarations have the cdecl/c calling
		// convention by default unless specified otherwise. Due to
		// foreign procedures do not have a body declared within this
		// code, you need append the --- symbol to the end to distinguish
		// it as a procedure literal without a body and not a procedure type.

		// The attributes system can be used to change specific properties
		// of entities declared within a block:

		@(default_calling_convention = "std")
		foreign kernel32 {
			@(link_name="GetLastError") get_last_error :: proc() -> i32 ---
		}

		// Example using the link_prefix attribute
		@(default_calling_convention = "std")
		@(link_prefix = "Get")
		foreign kernel32 {
			LastError :: proc() -> i32 ---
		}
	}
}

ranged_fields_for_array_compound_literals :: proc() {
	fmt.println("\n#ranged fields for array compound literals")
	{ // Normal Array Literal
		foo := [?]int{1, 4, 9, 16}
		fmt.println(foo)
	}
	{ // Indexed
		foo := [?]int{
			3 = 16,
			1 = 4,
			2 = 9,
			0 = 1,
		}
		fmt.println(foo)
	}
	{ // Ranges
		i := 2
		foo := [?]int {
			0 = 123,
			5..=9 = 54,
			10..<16 = i*3 + (i-1)*2,
		}
		#assert(len(foo) == 16)
		fmt.println(foo) // [123, 0, 0, 0, 0, 54, 54, 54, 54, 54, 8, 8, 8, 8, 8]
	}
	{ // Slice and Dynamic Array support
		i := 2
		foo_slice := []int {
			0 = 123,
			5..=9 = 54,
			10..<16 = i*3 + (i-1)*2,
		}
		assert(len(foo_slice) == 16)
		fmt.println(foo_slice) // [123, 0, 0, 0, 0, 54, 54, 54, 54, 54, 8, 8, 8, 8, 8]

		foo_dynamic_array := [dynamic]int {
			0 = 123,
			5..=9 = 54,
			10..<16 = i*3 + (i-1)*2,
		}
		assert(len(foo_dynamic_array) == 16)
		fmt.println(foo_dynamic_array) // [123, 0, 0, 0, 0, 54, 54, 54, 54, 54, 8, 8, 8, 8, 8]
	}
}

deprecated_attribute :: proc() {
	@(deprecated="Use foo_v2 instead")
	foo_v1 :: proc(x: int) {
		fmt.println("foo_v1")
	}
	foo_v2 :: proc(x: int) {
		fmt.println("foo_v2")
	}

	// NOTE: Uncomment to see the warning messages
	// foo_v1(1)
}

range_statements_with_multiple_return_values :: proc() {
	// IMPORTANT NOTE(bill, 2019-11-02): This feature is subject to be changed/removed
	fmt.println("\n#range statements with multiple return values")
	My_Iterator :: struct {
		index: int,
		data:  []i32,
	}
	make_my_iterator :: proc(data: []i32) -> My_Iterator {
		return My_Iterator{data = data}
	}
	my_iterator :: proc(it: ^My_Iterator) -> (val: i32, idx: int, cond: bool) {
		if cond = it.index < len(it.data); cond {
			val = it.data[it.index]
			idx = it.index
			it.index += 1
		}
		return
	}

	data := make([]i32, 6)
	for _, i in data {
		data[i] = i32(i*i)
	}

	{
		it := make_my_iterator(data)
		for val in my_iterator(&it) {
			fmt.println(val)
		}
	}
	{
		it := make_my_iterator(data)
		for val, idx in my_iterator(&it) {
			fmt.println(val, idx)
		}
	}
	{
		it := make_my_iterator(data)
		for {
			val, _, cond := my_iterator(&it)
			if !cond {
				break
			}
			fmt.println(val)
		}
	}
}


soa_struct_layout :: proc() {
	fmt.println("\n#SOA Struct Layout")

	{
		Vector3 :: struct {x, y, z: f32}

		N :: 2
		v_aos: [N]Vector3
		v_aos[0].x = 1
		v_aos[0].y = 4
		v_aos[0].z = 9

		fmt.println(len(v_aos))
		fmt.println(v_aos[0])
		fmt.println(v_aos[0].x)
		fmt.println(&v_aos[0].x)

		v_aos[1] = {0, 3, 4}
		v_aos[1].x = 2
		fmt.println(v_aos[1])
		fmt.println(v_aos)

		v_soa: #soa[N]Vector3

		v_soa[0].x = 1
		v_soa[0].y = 4
		v_soa[0].z = 9


		// Same syntax as AOS and treat as if it was an array
		fmt.println(len(v_soa))
		fmt.println(v_soa[0])
		fmt.println(v_soa[0].x)
		fmt.println(&v_soa[0].x)
		v_soa[1] = {0, 3, 4}
		v_soa[1].x = 2
		fmt.println(v_soa[1])

		// Can use SOA syntax if necessary
		v_soa.x[0] = 1
		v_soa.y[0] = 4
		v_soa.z[0] = 9
		fmt.println(v_soa.x[0])

		// Same pointer addresses with both syntaxes
		assert(&v_soa[0].x == &v_soa.x[0])


		// Same fmt printing
		fmt.println(v_aos)
		fmt.println(v_soa)
	}
	{
		// Works with arrays of length <= 4 which have the implicit fields xyzw/rgba
		Vector3 :: distinct [3]f32

		N :: 2
		v_aos: [N]Vector3
		v_aos[0].x = 1
		v_aos[0].y = 4
		v_aos[0].z = 9

		v_soa: #soa[N]Vector3

		v_soa[0].x = 1
		v_soa[0].y = 4
		v_soa[0].z = 9
	}
	{
		// SOA Slices
		// Vector3 :: struct {x, y, z: f32}
		Vector3 :: struct {x: i8, y: i16, z: f32}

		N :: 3
		v: #soa[N]Vector3
		v[0].x = 1
		v[0].y = 4
		v[0].z = 9

		s: #soa[]Vector3
		s = v[:]
		assert(len(s) == N)
		fmt.println(s)
		fmt.println(s[0].x)

		a := s[1:2]
		assert(len(a) == 1)
		fmt.println(a)

		d: #soa[dynamic]Vector3

		append_soa(&d, Vector3{1, 2, 3}, Vector3{4, 5, 9}, Vector3{-4, -4, 3})
		fmt.println(d)
		fmt.println(len(d))
		fmt.println(cap(d))
		fmt.println(d[:])
	}
	{ // soa_zip and soa_unzip
		fmt.println("\nsoa_zip and soa_unzip")

		x := []i32{1, 3, 9}
		y := []f32{2, 4, 16}
		z := []b32{true, false, true}

		// produce an #soa slice the normal slices passed
		s := soa_zip(a=x, b=y, c=z)

		// iterate over the #soa slice
		for v, i in s {
			fmt.println(v, i) // exactly the same as s[i]
			// NOTE: 'v' is NOT a temporary value but has a specialized addressing mode
			// which means that when accessing v.a etc, it does the correct transformation
			// internally:
			//         s[i].a === s.a[i]
			fmt.println(v.a, v.b, v.c)
		}

		// Recover the slices from the #soa slice
		a, b, c := soa_unzip(s)
		fmt.println(a, b, c)
	}
}

constant_literal_expressions :: proc() {
	fmt.println("\n#constant literal expressions")

	Bar :: struct {x, y: f32}
	Foo :: struct {a, b: int, using c: Bar}

	FOO_CONST :: Foo{b = 2, a = 1, c = {3, 4}}


	fmt.println(FOO_CONST.a)
	fmt.println(FOO_CONST.b)
	fmt.println(FOO_CONST.c)
	fmt.println(FOO_CONST.c.x)
	fmt.println(FOO_CONST.c.y)
	fmt.println(FOO_CONST.x) // using works as expected
	fmt.println(FOO_CONST.y)

	fmt.println("-------")

	ARRAY_CONST :: [3]int{1 = 4, 2 = 9, 0 = 1}

	fmt.println(ARRAY_CONST[0])
	fmt.println(ARRAY_CONST[1])
	fmt.println(ARRAY_CONST[2])

	fmt.println("-------")

	FOO_ARRAY_DEFAULTS :: [3]Foo{{}, {}, {}}
	fmt.println(FOO_ARRAY_DEFAULTS[2].x)

	fmt.println("-------")

	Baz :: enum{A=5, B, C, D}
	ENUM_ARRAY_CONST :: [Baz]int{.A ..= .C = 1, .D = 16}

	fmt.println(ENUM_ARRAY_CONST[.A])
	fmt.println(ENUM_ARRAY_CONST[.B])
	fmt.println(ENUM_ARRAY_CONST[.C])
	fmt.println(ENUM_ARRAY_CONST[.D])

	fmt.println("-------")

	Partial_Baz :: enum{A=5, B, C, D=16}
	#assert(len(Partial_Baz) < len(#partial [Partial_Baz]int))
	PARTIAL_ENUM_ARRAY_CONST :: #partial [Partial_Baz]int{.A ..= .C = 1, .D = 16}

	fmt.println(PARTIAL_ENUM_ARRAY_CONST[.A])
	fmt.println(PARTIAL_ENUM_ARRAY_CONST[.B])
	fmt.println(PARTIAL_ENUM_ARRAY_CONST[.C])
	fmt.println(PARTIAL_ENUM_ARRAY_CONST[.D])

	fmt.println("-------")


	STRING_CONST :: "Hellope!"

	fmt.println(STRING_CONST[0])
	fmt.println(STRING_CONST[2])
	fmt.println(STRING_CONST[3])

	fmt.println(STRING_CONST[0:5])
	fmt.println(STRING_CONST[3:][:4])
}

union_maybe :: proc() {
	fmt.println("\n#union #maybe")

	// NOTE: This is already built-in, and this is just a reimplementation to explain the behaviour
	Maybe :: union($T: typeid) #maybe {T}

	i: Maybe(u8)
	p: Maybe(^u8) // No tag is stored for pointers, nil is the sentinel value

	#assert(size_of(i) == size_of(u8) + size_of(u8))
	#assert(size_of(p) == size_of(^u8))

	i = 123
	x := i.?
	y, y_ok := p.?
	p = &x
	z, z_ok := p.?

	fmt.println(i, p)
	fmt.println(x, &x)
	fmt.println(y, y_ok)
	fmt.println(z, z_ok)
}

dummy_procedure :: proc() {
	fmt.println("dummy_procedure")
}

explicit_context_definition :: proc "c" () {
	// Try commenting the following statement out below
	context = runtime.default_context()

	fmt.println("\n#explicit context definition")
	dummy_procedure()
}

relative_data_types :: proc() {
	fmt.println("\n#relative data types")

	x: int = 123
	ptr: #relative(i16) ^int
	ptr = &x
	fmt.println(ptr^)

	arr := [3]int{1, 2, 3}
	s := arr[:]
	rel_slice: #relative(i16) []int
	rel_slice = s
	fmt.println(rel_slice)
	fmt.println(rel_slice[:])
	fmt.println(rel_slice[1])
}

or_else_operator :: proc() {
	fmt.println("\n#'or_else'")
	// IMPORTANT NOTE: 'or_else' is an experimental feature and subject to change/removal
	{
		m: map[string]int
		i: int
		ok: bool

		if i, ok = m["hellope"]; !ok {
			i = 123
		}
		// The above can be mapped to 'or_else'
		i = m["hellope"] or_else 123

		assert(i == 123)
	}
	{
		// 'or_else' can be used with type assertions too, as they
		// have optional ok semantics
		v: union{int, f64}
		i: int
		i = v.(int) or_else  123
		i = v.? or_else 123 // Type inference magic
		assert(i == 123)

		m: Maybe(int)
		i = m.? or_else 456
		assert(i == 456)
	}
}

or_return_operator :: proc() {
	fmt.println("\n#'or_return'")
	// IMPORTANT NOTE: 'or_return' is an experimental feature and subject to change/removal
	//
	// The concept of 'or_return' will work by popping off the end value in a multiple
	// valued expression and checking whether it was not 'nil' or 'false', and if so,
	// set the end return value to value if possible. If the procedure only has one
	// return value, it will do a simple return. If the procedure had multiple return
	// values, 'or_return' will require that all parameters be named so that the end
	// value could be assigned to by name and then an empty return could be called.

	Error :: enum {
		None,
		Something_Bad,
		Something_Worse,
		The_Worst,
		Your_Mum,
	}

	caller_1 :: proc() -> Error {
		return .None
	}

	caller_2 :: proc() -> (int, Error) {
		return 123, .None
	}
	caller_3 :: proc() -> (int, int, Error) {
		return 123, 345, .None
	}

	foo_1 :: proc() -> Error {
		// This can be a common idiom in many code bases
		n0, err := caller_2()
		if err != nil {
			return err
		}

		// The above idiom can be transformed into the following
		n1 := caller_2() or_return


		// And if the expression is 1-valued, it can be used like this
		caller_1() or_return
		// which is functionally equivalent to
		if err1 := caller_1(); err1 != nil {
			return err1
		}

		// Multiple return values still work with 'or_return' as it only
		// pops off the end value in the multi-valued expression
		n0, n1 = caller_3() or_return

		return .None
	}
	foo_2 :: proc() -> (n: int, err: Error) {
		// It is more common that your procedure turns multiple values
		// If 'or_return' is used within a procedure multiple parameters (2+),
		// then all the parameters must be named so that the remaining parameters
		// so that a bare 'return' statement can be used

		// This can be a common idiom in many code bases
		x: int
		x, err = caller_2()
		if err != nil {
			return
		}

		// The above idiom can be transformed into the following
		y := caller_2() or_return
		_ = y

		// And if the expression is 1-valued, it can be used like this
		caller_1() or_return

		// which is functionally equivalent to
		if err1 := caller_1(); err1 != nil {
			err = err1
			return
		}

		// If using a non-bare 'return' statement is required, setting the return values
		// using the normal idiom is a better choice and clearer to read.
		if z, zerr := caller_2(); zerr != nil {
			return -345 * z, zerr
		}

		// If the other return values need to be set depending on what the end value is,
		// the 'defer if' idiom is can be used
		defer if err != nil {
			n = -1
		}

		n = 123
		return
	}

	foo_1()
	foo_2()
}

arbitrary_precision_mathematics :: proc() {
	fmt.println("\n# core:math/big")

	print_bigint :: proc(name: string, a: ^big.Int, base := i8(10), print_name := true, newline := true, print_extra_info := true) {
		big.assert_if_nil(a)

		as, err := big.itoa(a, base)
		defer delete(as)

		cb := big.internal_count_bits(a)
		if print_name {
			fmt.printf(name)
		}
		if err != nil {
			fmt.printf(" (Error: %v) ", err)
		}
		fmt.printf(as)
		if print_extra_info {
		 	fmt.printf(" (base: %v, bits: %v, digits: %v)", base, cb, a.used)
		}
		if newline {
			fmt.println()
		}
	}

	a, b, c, d, e, f, res := &big.Int{}, &big.Int{}, &big.Int{}, &big.Int{}, &big.Int{}, &big.Int{}, &big.Int{}
	defer big.destroy(a, b, c, d, e, f, res)

	// How many bits should the random prime be?
	bits   := 64
	// Number of Rabin-Miller trials, -1 for automatic.
	trials := -1

	// Default prime generation flags
	flags := big.Primality_Flags{}

	err := big.internal_random_prime(a, bits, trials, flags)
	if err != nil {
		fmt.printf("Error %v while generating random prime.\n", err)
	} else {
		print_bigint("Random Prime A: ", a, 10)
		fmt.printf("Random number iterations until prime found: %v\n", big.RANDOM_PRIME_ITERATIONS_USED)
	}

	// If we want to pack this Int into a buffer of u32, how many do we need?
	count := big.internal_int_pack_count(a, u32)
	buf := make([]u32, count)
	defer delete(buf)

	written: int
	written, err = big.internal_int_pack(a, buf)
	fmt.printf("\nPacked into u32 buf: %v | err: %v | written: %v\n", buf, err, written)

	// If we want to pack this Int into a buffer of bytes of which only the bottom 6 bits are used, how many do we need?
	nails := 2

	count = big.internal_int_pack_count(a, u8, nails)
	byte_buf := make([]u8, count)
	defer delete(byte_buf)

	written, err = big.internal_int_pack(a, byte_buf, nails)
	fmt.printf("\nPacked into buf of 6-bit bytes: %v | err: %v | written: %v\n", byte_buf, err, written)



	// Pick another random big Int, not necesssarily prime.
	err = big.random(b, 2048)
	print_bigint("\n2048 bit random number: ", b)

	// Calculate GCD + LCM in one fell swoop
	big.gcd_lcm(c, d, a, b)

	print_bigint("\nGCD of random prime A and random number B: ", c)
	print_bigint("\nLCM of random prime A and random number B (in base 36): ", d, 36)
}

matrix_type :: proc() {
	fmt.println("\n# matrix type")
	// A matrix is a mathematical type built into Odin. It is a regular array of numbers,
	// arranged in rows and columns
	
	{
		// The following represents a matrix that has 2 rows and 3 columns
		m: matrix[2, 3]f32
		
		m = matrix[2, 3]f32{
			1, 9, -13,
			20, 5, -6,
		}
		
		// Element types of integers, float, and complex numbers are supported by matrices.
		// There is no support for booleans, quaternions, or any compound type.
		
		// Indexing a matrix can be used with the matrix indexing syntax
		// This mirrors othe type usages: type on the left, usage on the right
		
		elem := m[1, 2] // row 1, column 2
		assert(elem == -6)
		
		
		// Scalars act as if they are scaled identity matrices
		// and can be assigned to matrices as them
		b := matrix[2, 2]f32{}
		f := f32(3)
		b = f
		
		fmt.println("b", b)
		fmt.println("b == f", b == f)
		
	} 
	
	{ // Matrices support multiplication between matrices
		a := matrix[2, 3]f32{
			2, 3, 1,
			4, 5, 0,
		}
		
		b := matrix[3, 2]f32{
			1, 2,
			3, 4,
			5, 6,
		}
		
		fmt.println("a", a)
		fmt.println("b", b)
		
		c := a * b
		#assert(type_of(c) == matrix[2, 2]f32)
		fmt.tprintln("c = a * b", c)		
	}
	
	{ // Matrices support multiplication between matrices and arrays
		m := matrix[4, 4]f32{
			1, 2, 3, 4, 
			5, 5, 4, 2, 
			0, 1, 3, 0, 
			0, 1, 4, 1,
		}
		
		v := [4]f32{1, 5, 4, 3}
		
		// treating 'v' as a column vector
		fmt.println("m * v", m * v)
		
		// treating 'v' as a row vector
		fmt.println("v * m", v * m)
		
		// Support with non-square matrices
		s := matrix[2, 4]f32{ // [4][2]f32
			2, 4, 3, 1, 
			7, 8, 6, 5, 
		}
		
		w := [2]f32{1, 2}
		r: [4]f32 = w * s
		fmt.println("r", r)
	}
	
	{ // Component-wise operations 
		// if the element type supports it
		// Not support for '/', '%', or '%%' operations
		
		a := matrix[2, 2]i32{
			1, 2,
			3, 4,
		}
		
		b := matrix[2, 2]i32{
			-5,  1,
			 9, -7,
		}
		
		c0 := a + b
		c1 := a - b
		c2 := a & b
		c3 := a | b
		c4 := a ~ b
		c5 := a &~ b

		// component-wise multiplication
		// since a * b would be a standard matrix multiplication
		c6 := hadamard_product(a, b) 
		
		
		fmt.println("a + b",  c0)
		fmt.println("a - b",  c1)
		fmt.println("a & b",  c2)
		fmt.println("a | b",  c3)
		fmt.println("a ~ b",  c4)
		fmt.println("a &~ b", c5)
		fmt.println("hadamard_product(a, b)", c6)
	}
	
	{ // Submatrix casting square matrices
		// Casting a square matrix to another square matrix with same element type
		// is supported. 
		// If the cast is to a smaller matrix type, the top-left submatrix is taken.
		// If the cast is to a larger matrix type, the matrix is extended with zeros
		// everywhere and ones in the diagonal for the unfilled elements of the 
		// extended matrix.
		
		mat2 :: distinct matrix[2, 2]f32
		mat4 :: distinct matrix[4, 4]f32
		
		m2 := mat2{
			1, 3,
			2, 4,
		}
		
		m4 := mat4(m2)
		assert(m4[2, 2] == 1)
		assert(m4[3, 3] == 1)
		fmt.printf("m2 %#v\n", m2)
		fmt.println("m4", m4)
		fmt.println("mat2(m4)", mat2(m4))
		assert(mat2(m4) == m2)
		
		b4 := mat4{
			1, 2, 0, 0,
			3, 4, 0, 0,
			5, 0, 6, 0,
			0, 7, 0, 8,
		}
		fmt.println("b4", matrix_flatten(b4))
	}
	
	{ // Casting non-square matrices
		// Casting a matrix to another matrix is allowed as long as they share 
		// the same element type and the number of elements (rows*columns).
		// Matrices in Odin are stored in column-major order, which means
		// the casts will preserve this element order.
		
		mat2x4 :: distinct matrix[2, 4]f32
		mat4x2 :: distinct matrix[4, 2]f32
		
		x := mat2x4{
			1, 3, 5, 7, 
			2, 4, 6, 8,
		}
		
		y := mat4x2(x)
		fmt.println("x", x)
		fmt.println("y", y)
	}
	
	// TECHNICAL INFORMATION: the internal representation of a matrix in Odin is stored
	// in column-major format
	// e.g. matrix[2, 3]f32 is internally [3][2]f32 (with different a alignment requirement)
	// Column-major is used in order to utilize (SIMD) vector instructions effectively on 
	// modern hardware, if possible.
	//
	// Unlike normal arrays, matrices try to maximize alignment to allow for the (SIMD) vectorization
	// properties whilst keeping zero padding (either between columns or at the end of the type).
	// 
	// Zero padding is a compromise for use with third-party libraries, instead of optimizing for performance.
	// Padding between columns was not taken even if that would have allowed each column to be loaded 
	// individually into a SIMD register with the correct alignment properties. 
	// 
	// Currently, matrices are limited to a maximum of 16 elements (rows*columns), and a minimum of 1 element.
	// This is because matrices are stored as values (not a reference type), and thus operations on them will
	// be stored on the stack. Restricting the maximum element count minimizing the possibility of stack overflows.
	
	// Built-in Procedures (Compiler Level)
	// 	transpose(m)
	//		transposes a matrix
	// 	outer_product(a, b)
	// 		takes two array-like data types and returns the outer product
	//		of the values in a matrix
	// 	hadamard_product(a, b)
	// 		component-wise multiplication of two matrices of the same type
	// 	matrix_flatten(m)
	//		converts the matrix into a flatten array of elements
	//		in column-major order
	//		Example:
	//		m := matrix[2, 2]f32{
	//			x0, x1,
	//			y0, y1,	
	//		}
	//		array: [4]f32 = matrix_flatten(m)
	//		assert(array == {x0, y0, x1, y1})
	//	conj(x)
	//		conjugates the elements of a matrix for complex element types only
	
	// Built-in Procedures (Runtime Level) (all square matrix procedures)
	// 	determinant(m)
	// 	adjugate(m)
	// 	inverse(m)
	// 	inverse_transpose(m)
	// 	hermitian_adjoint(m)
	// 	matrix_trace(m)
	// 	matrix_minor(m)
}

main :: proc() {
	when true {
		the_basics()
		control_flow()
		named_proc_return_parameters()
		explicit_procedure_overloading()
		struct_type()
		union_type()
		using_statement()
		implicit_context_system()
		parametric_polymorphism()
		array_programming()
		map_type()
		implicit_selector_expression()
		partial_switch()
		cstring_example()
		bit_set_type()
		deferred_procedure_associations()
		reflection()
		quaternions()
		unroll_for_statement()
		where_clauses()
		foreign_system()
		ranged_fields_for_array_compound_literals()
		deprecated_attribute()
		range_statements_with_multiple_return_values()
		threading_example()
		soa_struct_layout()
		constant_literal_expressions()
		union_maybe()
		explicit_context_definition()
		relative_data_types()
		or_else_operator()
		or_return_operator()
		arbitrary_precision_mathematics()
		matrix_type()
	}
}