[Rd] Standalone Mathlib, C++ and ISNAN()

John W. Eaton jwe at bevo.che.wisc.edu
Thu Jan 6 05:31:25 CET 2005

On  6-Jan-2005, Bill Northcott <w.northcott at unsw.edu.au> wrote:

| On 06/01/2005, at 9:12 AM, Thomas Lumley wrote:
| >> It was suggested by one of the gcc people, but I could find no 
| >> documentation about it.  The ISO C++ docs do not include isnan as a 
| >> symbol provided by cmath within the std namespace.  I looked at the 
| >> gcc source code and could see no reason why it should work.
| >
| > Hmm.  What *are* C++ programmers supposed to use to test for NaN, 
| > then? It might well not be anything in the ISO standard, just as it 
| > isn't in C89, but surely there is some prescribed way to do it.
| I asked the same question.  So far I got no response.

What I finally decided to do for Octave was to use a C language
autoconf test for isnan, then provide a function declared "extern C"
that is a wrapper around the C isnan function (if it exists).  I also
use this method for other functions that may be easier to call from C
than directly from C++.


www.octave.org | www.che.wisc.edu/~jwe | Peace would shock and awe me.

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