Weekday.daysUntil

[dfrei]

Nice library !!

I think there is a little bug. The test fails for wed.daysUntil(.mon) and wed.daysUntil(.sun).

test "daysUntil" {
    const wed: Weekday = .wed;
    try std.testing.expectEqual(0, wed.daysUntil(.wed));
    try std.testing.expectEqual(6, wed.daysUntil(.tue));
    try std.testing.expectEqual(5, wed.daysUntil(.mon));
    try std.testing.expectEqual(4, wed.daysUntil(.sun));
}

Probably it has something to do with -% or +% because u3 has 8 values, not 7.

[rockorager]

Ooh good find. This is because the algorithm assumes a larger integer than a u3. It's relying on underflow to work: https://howardhinnant.github.io/date_algorithms.html#weekday_difference For Wednesday -> Monday, the math is: Monday (1) - Wednesday (3) = -2

…

-2 as a u3 = 6, but we are checking if the difference is <= 6 so we return 6 instead of adding 7. If we do this as a u8, -2 is 254. Add 7 with overflow, and we get 5.