Johan Råde wrote:
Impressive. You seem to have thought of everything. I'm just a bit concerned about efficiency. For instance, if I call your isnan and I use VC++, then the following happens:
1. _fpclass is called 2. a switch statement is called to translate the result 3. the translated result is compared against FP_NAN
Just doing x != x must be a lot faster, and works, at least on VC++ 7.1, even with compiler optimizations turned on.
I have situations where I want to check every element in an array with more than 100,000,000 elements, so I care about efficiency.
Understood, it's a question of getting a portable version - maybe an overly pessimistic version - and then adding optimisations for specific compilers where required. Actually MSVC has _isnan, so I really should be calling that :-) Likewise platforms that have an isnan macro should use it etc... John.