Re: Overfflow in Assert error messages

[Anonymouse via Digitalmars-d-learn]

On Thursday, 13 February 2020 at 07:49:13 UTC, Adnan wrote:
However my test fails saying something like:
source/binary_search.d(33): [unittest] 18446744073709551615 != 1
core.exception.AssertError@source/binary_search.d(33): 
18446744073709551615 != 1

What's causing this underflow?

It's ulong -1, which is the type idx is of on 64-bit systems. On 
32-bit systems it will be uint -1 and say "4294967295 != 0". 
indexOf is probably not doing what you think it's doing.

int indexOf(T)(const T[] list, const T key) {
    return -1;
}

void main()
{
    int[] arr = [ 0 ];
    foreach (idx, i; arr)
        assert(indexOf(arr, i) == idx);  // 18446744073709551615 
!= 0
}