Matthias Schabel wrote:
While porting the proposed Boost.Units (currently mcs::units) library to some (mainly older) platforms, we have run into problems with <cmath> functions being unavailable. For example, gcc 3.4.4 on Cygwin does not implement nexttoward, llrint, llround (possibly others). Given that the proposed fp utilities library already gives portable implementations of some TR1 functions in <cmath>, is it possible to extend support to provide a TR1 support for all functions aside from the special functions that John and Paul are working on providing?
Matthias _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
llrint: I don't see how to do a platform independent implementation. The function rounds to the nearest integer, using the current rounding direction. You get the current rounding direction using fegetround. It would be very hard to do a platform independent implementation of fegetround. I think it will be very hard to do platform independent implementations of any of the fe... functions in <cmath>. You probably need assembler to implement them at all. Does the Boost.Units library really need these functions? nextafter, nextbefore, nexttoward: Doable. To get the next floating point number after a given floating point number you copy the bits into an integer, add 1, and copy them back. You also need to do some special handling of 1: 0 2: std::numeric_limis<T>::min (if there are no denormals) 3: std::numeric_limits<max>::max 4: infinity 5: NaN If there is a need for this, I might do it, but not during the next two months. -- Johan Råde