Fernando Cacciola <[EMAIL PROTECTED]> wrote:
> Gabriel Dos Reis <[EMAIL PROTECTED]> wrote in
>> Yes. It is an incorrect (unfortunately popular)
>> implementation.
>>
> Right. We should say that more often. It is incorrect
> however popular.
>
> Most compilers provide a non standard extension for this
> purpose.
> 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.
Hi,
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:
g++2.95.3 (MinGW)
g++3.1 (MinGW)
Borland 5.5.1
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.
Thoughts?
--
Joel de Guzman
joel at boost-consulting.com
http://www.boost-consulting.com
http://spirit.sf.net
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