On Friday, 29 October 2021 at 14:20:09 UTC, Ali Çehreli wrote:
Unsigned!T abs(T)(const(T) x) if(isIntegral!T) { static if(isSigned!T) if(x < 0) return cast(Unsigned!T)-x; return x; }void main() { int a = -5; int b = -4; writeln(a + abs(b)); // -5 + 4 == -1? (No!) } The program prints uint.max.
This should be no surprise. You need to know what the resulting type of int + uint should be. And it is ...... uint! which is one of the stupit integer-promotion rules inherited from C. I just don't understand how "promoting" something by dropping some important information (the sign) and on the fly also destroying the absolute value can ever be a good choice. I always thought it should be the other way round. The way it is is like "promoting" int + float to int (by discarding the fraction part and possibly too high exponents). And those two types are also of same size, so this is not an argument. Promotion should always be in a direction where it at least sometimes can be correct.
