From: Joel de Guzman (djowel_at_[hidden])
Date: 2003-07-05 07:27:31
Fernando Cacciola <fernando_cacciola_at_[hidden]> wrote:
> Gabriel Dos Reis <gdr_at_[hidden]> wrote in
>> Yes. It is an incorrect (unfortunately popular)
> Right. We should say that more often. It is incorrect
> however popular.
> Most compilers provide a non standard extension for this
> For instance, Borland uses _isnan.
> In general, these extensions are found on <float>.
> The best approach, IMO, is to have a boost::is_nan() with
> compiler specific implementations.
We have an is_nan(float) implementation (for quiet NaNs of course)
that does just that. Right now, it supports most compilers on Win32 but it
should be straight-forward to support others. Right now, it is tested on:
Comeau 4.24 (Win32)
Microsoft Visual C++ 6
Microsoft Visual C++ 7
Microsoft Visual C++ 7.1
Metrowerks CodeWarrior 7.2
The default implementation assumes IEEE754 floating point. It takes advantage
of the fact that IEEE754 has a well defined binary layout for quiet NaNs. Platform
specific implementations forward the call to the correct platform header when
available. The code does not rely on the availability of numeric_limits.
I hope this can be used as the basis of a standardized boost::is_nan utility.
-- Joel de Guzman joel at boost-consulting.com http://www.boost-consulting.com http://spirit.sf.net
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk