zig/test/cases/array.zig

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

test "arrays" {
    var array: [5]u32 = undefined;

    var i: u32 = 0;
    while (i < 5) {
        array[i] = i + 1;
        i = array[i];
    }

    i = 0;
    var accumulator = u32(0);
    while (i < 5) {
        accumulator += array[i];

        i += 1;
    }

    assert(accumulator == 15);
    assert(getArrayLen(array) == 5);
}
fn getArrayLen(a: []const u32) usize {
    return a.len;
}

test "void arrays" {
    var array: [4]void = undefined;
    array[0] = void{};
    array[1] = array[2];
    assert(@sizeOf(@typeOf(array)) == 0);
    assert(array.len == 4);
}

test "array literal" {
    const hex_mult = []u16{
        4096,
        256,
        16,
        1,
    };

    assert(hex_mult.len == 4);
    assert(hex_mult[1] == 256);
}

test "array dot len const expr" {
    assert(comptime x: {
        break :x some_array.len == 4;
    });
}

const ArrayDotLenConstExpr = struct {
    y: [some_array.len]u8,
};
const some_array = []u8{
    0,
    1,
    2,
    3,
};

test "nested arrays" {
    const array_of_strings = [][]const u8{
        "hello",
        "this",
        "is",
        "my",
        "thing",
    };
    for (array_of_strings) |s, i| {
        if (i == 0) assert(mem.eql(u8, s, "hello"));
        if (i == 1) assert(mem.eql(u8, s, "this"));
        if (i == 2) assert(mem.eql(u8, s, "is"));
        if (i == 3) assert(mem.eql(u8, s, "my"));
        if (i == 4) assert(mem.eql(u8, s, "thing"));
    }
}

var s_array: [8]Sub = undefined;
const Sub = struct {
    b: u8,
};
const Str = struct {
    a: []Sub,
};
test "set global var array via slice embedded in struct" {
    var s = Str{ .a = s_array[0..] };

    s.a[0].b = 1;
    s.a[1].b = 2;
    s.a[2].b = 3;

    assert(s_array[0].b == 1);
    assert(s_array[1].b == 2);
    assert(s_array[2].b == 3);
}

test "array literal with specified size" {
    var array = [2]u8{
        1,
        2,
    };
    assert(array[0] == 1);
    assert(array[1] == 2);
}

test "array child property" {
    var x: [5]i32 = undefined;
    assert(@typeOf(x).Child == i32);
}

test "array len property" {
    var x: [5]i32 = undefined;
    assert(@typeOf(x).len == 5);
}

test "array len field" {
    var arr = [4]u8{ 0, 0, 0, 0 };
    var ptr = &arr;
    assert(arr.len == 4);
    comptime assert(arr.len == 4);
    assert(ptr.len == 4);
    comptime assert(ptr.len == 4);
}

test "single-item pointer to array indexing and slicing" {
    testSingleItemPtrArrayIndexSlice();
    comptime testSingleItemPtrArrayIndexSlice();
}

fn testSingleItemPtrArrayIndexSlice() void {
    var array = "aaaa";
    doSomeMangling(&array);
    assert(mem.eql(u8, "azya", array));
}

fn doSomeMangling(array: *[4]u8) void {
    array[1] = 'z';
    array[2..3][0] = 'y';
}

test "implicit cast single-item pointer" {
    testImplicitCastSingleItemPtr();
    comptime testImplicitCastSingleItemPtr();
}

fn testImplicitCastSingleItemPtr() void {
    var byte: u8 = 100;
    const slice = (*[1]u8)(&byte)[0..];
    slice[0] += 1;
    assert(byte == 101);
}