Paul A Bristow wrote:
Does anyone have a ***portable*** version of macro signbit (C99)
or can we combine versions that work on each compiler/hardware/endian...
or an equivalent C++ function, perhaps called is_negative?
(This would just test the signbit for the type(s)).
There are several places where this would be useful in dealing properly with NaNs and zero and infinity etc.
Thanks
Paul
PS Must be Boost license of course.
How about bool is_negative(float x) { const float one = 1; const float neg_one = -1; const int one_bits = reinterpret_cast<const int&>(one); const int neg_one_bits = reinterpret_cast<const int&>(neg_one); const int sign_mask = one_bits ^ neg_one_bits; return reinterpret_cast<int&>(x) & sign_mask; } --Johan Råde