4 POSIX specification: @url{http://www.opengroup.org/susv3xbd/math.h.html}
8 Portability problems fixed by Gnulib:
11 The macro @code{NAN} is not defined on some platforms:
12 OpenBSD 4.0, AIX 5.1, IRIX 6.5, OSF/1 5.1, Solaris 10.
15 Portability problems not fixed by Gnulib:
18 @code{NAN} is not a compile time constant with some compilers:
19 OSF/1 with Compaq (ex-DEC) C 6.4.