Always false float comparisons

[Max Samukha via Digitalmars-d]

On Monday, 16 May 2016 at 04:02:54 UTC, Manu wrote:

> extended x = 1.3;
> x + y;
>
> If that code were to CTFE, I expect the CTFE to use extended 
> precision.
> My point is, CTFE should surely follow the types and language
> semantics as if it were runtime generated code... It's not 
> reasonable
> that CTFE has higher precision applied than the same code at 
> runtime.
> CTFE must give the exact same result as runtime execution of 
> the function.
>

You are not even guaranteed to get the same result on two 
different x86 implementations. AMD64:

"The processor produces a floating-point result defined by the 
IEEE standard to be infinitely precise.
This result may not be representable exactly in the destination 
format, because only a subset of the
continuum of real numbers finds exact representation in any 
particular floating-point format."