odin-lang.Odin/misc/old_demos/demo007.odin

import "core:fmt.odin"
import "core:strconv.odin"
import "core:mem.odin"
import "core:bits.odin"
import "core:hash.odin"
import "core:math.odin"
import "core:os.odin"
import "core:raw.odin"
import "core:sort.odin"
import "core:strings.odin"
import "core:types.odin"
import "core:utf16.odin"
import "core:utf8.odin"

when ODIN_OS == "windows" {
	import "core:atomics.odin"
	import "core:opengl.odin"
	import "core:thread.odin"
	import win32 "core:sys/windows.odin"
}

general_stuff :: proc() {
	{ // `do` for inline statmes rather than block
		foo :: proc() do fmt.println("Foo!");
		if   false do foo();
		for  false do foo();
		when false do foo();

		if false do foo();
		else     do foo();
	}

	{ // Removal of `++` and `--` (again)
		x: int;
		x += 1;
		x -= 1;
	}
	{ // Casting syntaxes
		i := i32(137);
		ptr := &i;

		fp1 := (^f32)(ptr);
		// ^f32(ptr) == ^(f32(ptr))
		fp2 := cast(^f32)ptr;

		f1 := (^f32)(ptr)^;
		f2 := (cast(^f32)ptr)^;

		// Questions: Should there be two ways to do it?
	}

	/*
	 * Remove *_val_of built-in procedures
	 * size_of, align_of, offset_of
	 * type_of, type_info_of
	 */

	{ // `expand_to_tuple` built-in procedure
		Foo :: struct {
			x: int,
			b: bool,
		}
		f := Foo{137, true};
		x, b := expand_to_tuple(f);
		fmt.println(f);
		fmt.println(x, b);
		fmt.println(expand_to_tuple(f));
	}

	{
		// ..  half-closed range
		// .. open range

		for in 0..2  {} // 0, 1
		for in 0..2 {} // 0, 1, 2
	}
}

default_struct_values :: proc() {
	{
		Vector3 :: struct {
			x: f32,
			y: f32,
			z: f32,
		}
		v: Vector3;
		fmt.println(v);
	}
	{
		// Default values must be constants
		Vector3 :: struct {
			x: f32 = 1,
			y: f32 = 4,
			z: f32 = 9,
		}
		v: Vector3;
		fmt.println(v);

		v = Vector3{};
		fmt.println(v);

		// Uses the same semantics as a default values in a procedure
		v = Vector3{137};
		fmt.println(v);

		v = Vector3{z = 137};
		fmt.println(v);
	}

	{
		Vector3 :: struct {
			x := 1.0,
			y := 4.0,
			z := 9.0,
		}
		stack_default: Vector3;
		stack_literal := Vector3{};
		heap_one      := new(Vector3);         defer free(heap_one);
		heap_two      := new_clone(Vector3{}); defer free(heap_two);

		fmt.println("stack_default - ", stack_default);
		fmt.println("stack_literal - ", stack_literal);
		fmt.println("heap_one      - ", heap_one^);
		fmt.println("heap_two      - ", heap_two^);


		N :: 4;
		stack_array: [N]Vector3;
		heap_array := new([N]Vector3);    defer free(heap_array);
		heap_slice := make([]Vector3, N); defer free(heap_slice);
		fmt.println("stack_array[1] - ", stack_array[1]);
		fmt.println("heap_array[1]  - ", heap_array[1]);
		fmt.println("heap_slice[1]  - ", heap_slice[1]);
	}
}




union_type :: proc() {
	{
		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 :: struct {x, y, z: f32};
	Quaternion :: struct {x, y, z: f32, w: f32 = 1};

	// 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: type) -> ^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  do fmt.println("Robotic");
			if e.is_zombie do fmt.println("Grrrr!");
		}
	}

	{
		// 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: type) -> ^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  do fmt.println("Robotic");
			if e.is_zombie do 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;
			}
		*/
	}
}

parametric_polymorphism :: proc() {
	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: type) -> ^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: type) {
			occupied: bool,
			hash:     u32,
			key:      Key,
			value:    Value,
		}
		TABLE_SIZE_MIN :: 32;
		Table :: struct(Key, Value: type) {
			count:     int,
			allocator: Allocator,
			slots:     []Table_Slot(Key, Value),
		}

		// Only allow types that are specializations of a (polymorphic) slice
		make_slice :: proc(T: type/[]$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 do c.allocator = table.allocator;

			push_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 do c.allocator = table.allocator;

			push_context c {
				old_slots := table.slots;

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

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

				free(old_slots);
			}
		}

		// 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(cap(table.slots)) {
					expand(table);
				}
				assert(table.count <= cap(table.slots));

				hash := get_hash(key);
				index = int(hash % u32(cap(table.slots)));

				for table.slots[index].occupied {
					if index += 1; index >= cap(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 cap(table.slots) <= 0 do return -1;

			index := int(hash % u32(cap(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 >= cap(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 do put(&table, "Hellope", i);
		for i in 0..42 do 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
	}
}




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

threading_example :: proc() {
	when ODIN_OS == "windows" {
		unordered_remove :: proc(array: ^[]$T, index: int, loc := #caller_location) {
			__bounds_check_error_loc(loc, index, len(array));
			array[index] = array[len(array)-1];
			pop(array);
		}
		ordered_remove :: proc(array: ^[]$T, index: int, loc := #caller_location) {
			__bounds_check_error_loc(loc, index, len(array));
			copy(array[index..], array[index+1..]);
			pop(array);
		}

		worker_proc :: proc(t: ^thread.Thread) -> int {
			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);
				// win32.sleep(1);
			}
			return 0;
		}

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

		for i in 0..len(prefix_table) {
			if t := thread.create(worker_proc); t != nil {
				t.init_context = context;
				t.use_init_context = true;
				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;
				}
			}
		}
	}
}

main :: proc() {
	when false {
		fmt.println("\n# general_stuff");              general_stuff();
		fmt.println("\n# default_struct_values");      default_struct_values();
		fmt.println("\n# union_type");                 union_type();
		fmt.println("\n# parametric_polymorphism");    parametric_polymorphism();
		fmt.println("\n# threading_example");          threading_example();
	}
}