# Arrays

const expect = @import("std").testing.expect;
const assert = @import("std").debug.assert;
const mem = @import("std").mem;

// array literal
const message = [_]u8{ 'h', 'e', 'l', 'l', 'o' };

// alternative initialization using result location
const alt_message: [5]u8 = .{ 'h', 'e', 'l', 'l', 'o' };

comptime {
    assert(mem.eql(u8, &message, &alt_message));
}

// get the size of an array
comptime {
    assert(message.len == 5);
}

// A string literal is a single-item pointer to an array.
const same_message = "hello";

comptime {
    assert(mem.eql(u8, &message, same_message));
}

test "iterate over an array" {
    var sum: usize = 0;
    for (message) |byte| {
        sum += byte;
    }
    try expect(sum == 'h' + 'e' + 'l' * 2 + 'o');
}

// modifiable array
var some_integers: [100]i32 = undefined;

test "modify an array" {
    for (&some_integers, 0..) |*item, i| {
        item.* = @intCast(i);
    }
    try expect(some_integers[10] == 10);
    try expect(some_integers[99] == 99);
}

// array concatenation works if the values are known
// at compile time
const part_one = [_]i32{ 1, 2, 3, 4 };
const part_two = [_]i32{ 5, 6, 7, 8 };
const all_of_it = part_one ++ part_two;
comptime {
    assert(mem.eql(i32, &all_of_it, &[_]i32{ 1, 2, 3, 4, 5, 6, 7, 8 }));
}

// remember that string literals are arrays
const hello = "hello";
const world = "world";
const hello_world = hello ++ " " ++ world;
comptime {
    assert(mem.eql(u8, hello_world, "hello world"));
}

// ** does repeating patterns
const pattern = "ab" ** 3;
comptime {
    assert(mem.eql(u8, pattern, "ababab"));
}

// initialize an array to zero
const all_zero = [_]u16{0} ** 10;

comptime {
    assert(all_zero.len == 10);
    assert(all_zero[5] == 0);
}

// use compile-time code to initialize an array
var fancy_array = init: {
    var initial_value: [10]Point = undefined;
    for (&initial_value, 0..) |*pt, i| {
        pt.* = Point{
            .x = @intCast(i),
            .y = @intCast(i * 2),
        };
    }
    break :init initial_value;
};
const Point = struct {
    x: i32,
    y: i32,
};

test "compile-time array initialization" {
    try expect(fancy_array[4].x == 4);
    try expect(fancy_array[4].y == 8);
}

// call a function to initialize an array
var more_points = [_]Point{makePoint(3)} ** 10;
fn makePoint(x: i32) Point {
    return Point{
        .x = x,
        .y = x * 2,
    };
}
test "array initialization with function calls" {
    try expect(more_points[4].x == 3);
    try expect(more_points[4].y == 6);
    try expect(more_points.len == 10);
}

$ zig test test_arrays.zig
1/4 test_arrays.test.iterate over an array...OK
2/4 test_arrays.test.modify an array...OK
3/4 test_arrays.test.compile-time array initialization...OK
4/4 test_arrays.test.array initialization with function calls...OK
All 4 tests passed.

const std = @import("std");
const expect = std.testing.expect;
const expectEqual = std.testing.expectEqual;

const mat4x5 = [4][5]f32{
    [_]f32{ 1.0, 0.0, 0.0, 0.0, 0.0 },
    [_]f32{ 0.0, 1.0, 0.0, 1.0, 0.0 },
    [_]f32{ 0.0, 0.0, 1.0, 0.0, 0.0 },
    [_]f32{ 0.0, 0.0, 0.0, 1.0, 9.9 },
};
test "multidimensional arrays" {
    // mat4x5 itself is a one-dimensional array of arrays.
    try expectEqual(mat4x5[1], [_]f32{ 0.0, 1.0, 0.0, 1.0, 0.0 });

    // Access the 2D array by indexing the outer array, and then the inner array.
    try expect(mat4x5[3][4] == 9.9);

    // Here we iterate with for loops.
    for (mat4x5, 0..) |row, row_index| {
        for (row, 0..) |cell, column_index| {
            if (row_index == column_index) {
                try expect(cell == 1.0);
            }
        }
    }

    // Initialize a multidimensional array to zeros.
    const all_zero: [4][5]f32 = .{.{0} ** 5} ** 4;
    try expect(all_zero[0][0] == 0);
}

$ zig test test_multidimensional_arrays.zig
1/1 test_multidimensional_arrays.test.multidimensional arrays...OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "0-terminated sentinel array" {
    const array = [_:0]u8{ 1, 2, 3, 4 };

    try expect(@TypeOf(array) == [4:0]u8);
    try expect(array.len == 4);
    try expect(array[4] == 0);
}

test "extra 0s in 0-terminated sentinel array" {
    // The sentinel value may appear earlier, but does not influence the compile-time 'len'.
    const array = [_:0]u8{ 1, 0, 0, 4 };

    try expect(@TypeOf(array) == [4:0]u8);
    try expect(array.len == 4);
    try expect(array[4] == 0);
}

$ zig test test_null_terminated_array.zig
1/2 test_null_terminated_array.test.0-terminated sentinel array...OK
2/2 test_null_terminated_array.test.extra 0s in 0-terminated sentinel array...OK
All 2 tests passed.

const print = @import("std").debug.print;

fn swizzleRgbaToBgra(rgba: [4]u8) [4]u8 {
    // readable swizzling by destructuring
    const r, const g, const b, const a = rgba;
    return .{ b, g, r, a };
}

pub fn main() void {
    const pos = [_]i32{ 1, 2 };
    const x, const y = pos;
    print("x = {}, y = {}\n", .{x, y});

    const orange: [4]u8 = .{ 255, 165, 0, 255 };
    print("{any}\n", .{swizzleRgbaToBgra(orange)});
}

$ zig build-exe destructuring_arrays.zig
$ ./destructuring_arrays
x = 1, y = 2
{ 0, 165, 255, 255 }