On Tuesday, 24 October 2017 at 01:22:57 UTC, codephantom wrote:
On Monday, 23 October 2017 at 21:51:24 UTC, Basile B. wrote:
---
/**
* Wraps a floating point type that doesn't follow D
permissive float conversion
* rules.
*
* In D, as in C++, implicit conversion from $(D double) to
$(D float) is allowed,
* leading to a possible precision loss. This can't happen
when using this wrapper.
*/
Want to hammer in a nail.. just go ahead and use a bulldozer ;-)
Simple things should be simple.
I cannot see how the simplest solution would be any other than
to have a compiler option for warning you of implicit
conversions.
I'm gonna propose the change in a PR. But I already see
problems...
One may call a trigo function with the highest precision possible
so that the FP coprocessor get more accurate internally. The
result, even if converted from real to float is better. This is
exactly what happens here:
https://github.com/dlang/phobos/pull/5804/files#diff-f127f38af25baf8333b65fa51824b92fR3037
To be clear, w/ the patch a warning is emitted for the first cos:
void main()
{
import std.math;
float f0 = cos(2 * PI / 1.123548789545545646452154L);
float f1 = cos(cast(float)(2 * PI /
1.123548789545545646452154L));
writefln("%.8g - %.8g", f0, f1);
}
but paradoxically the first is more accurate.
