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

From: John W. Eaton <>
Date: Thu 06 Jan 2005 - 15:31:25 EST

On 6-Jan-2005, Bill Northcott <> 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++.


-- | | Peace would shock and awe me.

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