Opinions: The Best and Worst of D (for a lecture/talk I intend to give)

[anonymous via Digitalmars-d-learn]

On Wednesday, 9 July 2014 at 17:13:21 UTC, H. S. Teoh via
Digitalmars-d-learn wrote:
> For the comparison s < u, where s is a signed value and u is an 
> unsigned
> value, whenever s is negative, the return value of opCmp must be
> negative.  Assuming 2's-complement representation of integers, 
> this
> means we simply copy the MSB of s (i.e., the sign bit) to the 
> result. So
> we can implement s < u as:
>
> 	enum signbitMask = 1u << (s.sizeof*8 - 1); // this is a 
> compile-time constant
> 	return (s - u) | (s & signbitMask); // look ma, no branches!

This is a problem, isn't it:

void main()
{
      assert(cmp(0, uint.max) < 0); /* fails */
}
int cmp(int s, uint u)
{
      enum signbitMask = 1u << (s.sizeof*8 - 1); // this is a
compile-time constant
      return (s - u) | (s & signbitMask); // look ma, no branches!
}