Re: isnan in fortran

[Michael Goffioul]

On Tue, Apr 10, 2012 at 2:03 PM, Jordi Gutiérrez Hermoso
<address@hidden> wrote:
> On 10 April 2012 08:28, Mike Miller <address@hidden> wrote:
>> On Tue, Apr 10, 2012 at 12:44:07PM +0200, c. wrote:
>>> I am regularly building Octave on OSX withg gcc/gfortran 4.2.1
>>> [...]
>>> I need to locally apply the following patch (which I keep in my hq
>>> patch queue), as gfortran 4.2 does not have isnan:
>>> [...]
>>> Does anyone know a cleaner and portable way how these functions
>>> could be made to work with fortran compilers that do not have
>>> ISNAN?
>>
>> I run into the same problem, RHEL 5.x with gcc 4.1.2.
> [snip]
>> A quick search suggests (X.NE.X) may be the best alternative, at
>> least for IEEE 754 systems.
>
> Can Fortran be preprocessed? If so, can we write an autoconf macro to
> check for isnan and use X.NE.X if not?

http://gcc.gnu.org/onlinedocs/gfortran/Preprocessing-Options.html

Apparently, it can be preprocessed, but it's not enabled by default
for .f files (assuming .f extension is treated differently than .F,
which is not clear from the documentation).

Michael.