lang/zig/while-unpack.zig


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

var numbers_left: u32 = undefined;

fn eventuallyNullSequence() ?u32 {
    return if (numbers_left == 0) null else blk: {
        numbers_left -= 1;
        break :blk numbers_left;
    };
}

fn eventuallyErrorSequence() anyerror!u32 {
    return if (numbers_left == 0) error.ReachedZero else blk: {
        numbers_left -= 1;
        break :blk numbers_left;
    };
}

test "while null capture" {
    var sum1: u32 = 0;
    numbers_left = 3;
    while (eventuallyNullSequence()) |value|
        sum1 += value;
    expect(sum1 == 3);

    var sum2: u32 = 0;
    numbers_left = 3;
    while (eventuallyNullSequence()) |value| {
        sum2 += value;
    } else {
        expect(sum2 == 3);
    }
}

test "while error union capture" {
    var sum: u32 = 0;
    numbers_left = 3;
    while (eventuallyErrorSequence()) |value| {
        sum += value;
    } else |err| {
        expect(err == error.ReachedZero);
    }
}