#include "Config/config.h" #if HAVE_ISNAN_IN_MATH_H
# include <math.h> #elif HAVE_ISNAN_IN_CMATH
# include <cmath> #elif HAVE_STD_ISNAN_IN_CMATH
# include <cmath>
using std::isnan; #else
# error "Don't know how to get isnan()" #endif
so one of the following is true for your platform:
1. The compiler is not finding <cmath> (doubt it)
2. The HAVE_ISNAN_IN_CMATH or HAVE_STD_ISNAN_IN_CMATH #defines are not
being set in Config/config.h (likely)
Since it is likely the #defines are not set, you can do one of two things:
1. Discover why the configure script doesn't recognize your platform as
having a cmath header and fix it.
2. Fix (in build dir) your include/Config/config.h so that the
HAVE_ISNAN_IN_CMATH variable is set to 1. note that this is a generated
file (source is include/Config/config.h.in) but you can override the
settings by changing it in your build directory.