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Re: NaN values in c++

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Marc <marc.glisse@gmail.com> writes:
>> You just have to document requirements very cleary, e.g. "this library 
>> requires IEEE 754 conformance, don't use e.g. -fastmath option".
...
>> Happily the C++11 standard, by incorporating most of the C99 standard 
>> library, requires a common isnan() function:
>
> I don't see how that changes anything. -ffinite-math-only (implied by
> -ffast-math) is a way for the user to say that there won't be a NaN
> (or an infinity) anywhere. That flag is then likely to replace isnan
> with a function that always returns false.

... and indeed that does happen in gcc.

One could probably get around this in practice by using one's own
external "really_is_nan" function, making sure that it's compiled
without -ffast-math or whatever...

-Miles

-- 
Quidquid latine dictum sit, altum viditur.

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Thread

NaN values in c++ Luca Cerone <luca.cerone@gmail.com> - 2012-03-02 01:24 -0800
  Re: NaN values in c++ "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2012-03-02 11:43 +0100
    Re: NaN values in c++ Marc <marc.glisse@gmail.com> - 2012-03-02 11:33 +0000
      Re: NaN values in c++ Luca Cerone <luca.cerone@gmail.com> - 2012-03-02 08:01 -0800
        Re: NaN values in c++ Paavo Helde <myfirstname@osa.pri.ee> - 2012-03-02 11:14 -0600
      Re: NaN values in c++ Miles Bader <miles@gnu.org> - 2012-03-03 07:35 +0900

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