Always false float comparisons

[Ola Fosheim Grøstad via Digitalmars-d]

On Sunday, 15 May 2016 at 22:34:24 UTC, Walter Bright wrote:
> So far, nobody has posted a legitimate one (i.e. not contrived).

Oh, so comparing the exact same calculation, using the exact same 
binary executable function, is  not a legitimate algorithm. It is 
the most trivial thing to do and rather common. It should be 
_very_ convincing.

But hey, here is another one:

const real x = f();
assert(0<=x && x<1);
x += 1;

const float f32 = cast(float)(x);
const real residue = x - cast(real)f32; // ZERO!!!!

output(dither(f32, residue)); // DITHERING IS FUBAR!!!