On 8/26/2014 12:24 AM, Don wrote:
On Monday, 25 August 2014 at 23:29:21 UTC, Walter Bright wrote:
On 8/25/2014 4:15 PM, "Ola Fosheim Grøstad"
<[email protected]>" wrote:
On Monday, 25 August 2014 at 21:24:11 UTC, Walter Bright wrote:
I didn't know that. But recall I did implement it in DMC++, and it turned out
to simply not be useful. I'd be surprised if the new C++ support for it does
anything worthwhile.
Well, one should initialize with signaling NaN. Then you get an exception if you
try to compute using uninitialized values.
That's the theory. The practice doesn't work out so well.
To be more concrete:
Processors from AMD have signalling NaN behaviour which is different from
processors from Intel.
And the situation is worst on most other architectures. It's a lost cause, I
think.
The other issues were just when the snan => qnan conversion took place. This is
quite unclear given the extensive constant folding, CTFE, etc., that D does.
It was also affected by how dmd generates code. Some code gen on floating point
doesn't need the FPU, such as toggling the sign bit. But then what happens with
snan => qnan?
The whole thing is an undefined, unmanageable mess.
