On Sunday, 15 May 2016 at 22:49:27 UTC, Walter Bright wrote:
On 5/15/2016 2:06 PM, Ola Fosheim Grøstad wrote:
The net result is that adding const/immutable to a type can
change the semantics
of the program entirely at the whim of the compiler
implementor.
C++ Standard allows the same increased precision, at the whim
of the compiler implementor, as quoted to you earlier.
What your particular C++ compiler does is not relevant, as its
behavior is not required by the Standard.
This is a crazy attitude to take. C++ provides means to detect
that IEEE floats are being used in the standard library. C/C++
supports non-standard floating point because some platforms only
provide non-standard floating point. They don't do it because it
is _desirable_ in general.
You might as well say that you are not required to drive on the
right side on the road, because you occasionally have to drive on
the left. So therefore it is ok to always drive on left.
My proposal removes the "whim" by requiring 128 bit precision
for CTFE.
No, D's take on floating point is FUBAR.
const float value = 1.30;
float copy = value;
assert(value*0.5 == copy*0.5); // FAILS! => shutdown
