Why do I get isinf undefined when linking with libdps on Solaris 2.3?

That's a bug in libdps (fixed in 2.4). Sun compiles and links its
software with its own compilers. The isinf() function is shipped
with the SunPRO compilers, but not defined in any Solaris 2.3

A workaround exists, and consists of adding the following to
your program:

#include <ieeefp.h>

int isinf(double x) { return !finite(x) && x==x; }

[an error occurred while processing this directive]