Re: Slaying the HYPOTamus

On Sun, Aug 23, 2009 at 07:42, Tom Lane<tgl@sss.pgh.pa.us> wrote:
> Greg Stark <gsstark@mit.edu> writes:
>> If there's a performance advantage then we could add a configure test
>> and define the macro to call hypot(). You said it existed before C99
>> though, how widespread was it? If it's in all the platforms we support
>> it might be reasonable to just go with it.
>
> For one data point, I see hypot() in HPUX 10.20, released circa 1996.
> I suspect we would want a configure test and a substitute function
> anyway.  Personally I wouldn't have a problem with the substitute being
> the naive sqrt(x*x+y*y), particularly if it's replacing existing code
> that overflows in the same places.

For another data point, Microsoft documentation says:
"This POSIX function is deprecated beginning in Visual C++ 2005. Use
the ISO C++ conformant  _hypot instead."

_hypot() has been there since Windows 95, so it shouldn't be a problem
to use it - it just needs a define, like we have for some other such
functions.

-- Magnus HaganderMe: http://www.hagander.net/Work: http://www.redpill-linpro.com/