On 16 May 2016 at 10:25, Ola Fosheim Grøstad via Digitalmars-d <digitalmars-d@puremagic.com> wrote: > On Monday, 16 May 2016 at 07:54:32 UTC, Iain Buclaw wrote: >> >> On 16 May 2016 at 09:22, Ola Fosheim Grøstad via Digitalmars-d >> <digitalmars-d@puremagic.com> wrote: >>> >>> On Monday, 16 May 2016 at 06:34:04 UTC, Iain Buclaw wrote: >>> >>> No, promoting to double is ok. >> >> >> Your own example: >> >> const float value = 1.30; >> float copy = value; >> assert(value*0.5 == copy*0.5); >> >> Versus how you'd expect it to work. >> >> const float value = 1.30; >> float copy = value; >> assert(cast(float)(value*0.5) == cast(float)(copy*0.5)); // Compare >> as float, not double. > > > Promoting to double is sound. That is not the issue. Just replace the assert > with a function like "check(real x, real y)". The programmer shouldn't have > to look it up. Using "check(real x, real y)" should _not_ give a different > result than using "check(float x, float y)". If you have implemented the > former, you shouldn't have to implement the latter to get reasonable > results. > > Binding to "const float" or "float" should not change the outcome. > > The problem is not the promotion, the problem is that you don't get the > coercion to 32 bit floats where you requested it. This violates the > principle of "least surprise". >
But you *didn't* request coercion to 32 bit floats. Otherwise you would have used 1.30f.
