NAN(3)			   Linux Programmers Manual		       NAN(3)



NAME
       nan, nanf, nanl - return Not a Number

SYNOPSIS
       #include 

       double nan(const char *tagp);
       float nanf(const char *tagp);
       long double nanl(const char *tagp);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       nan(),  nanf(),	nanl():  _XOPEN_SOURCE >= 600  ||  _ISOC99_SOURCE;  or
       cc -std=c99

DESCRIPTION
       These functions return a representation (determined by tagp) of a quiet
       NaN.   If  the  implementation does not support quiet NaNs, these func
       tions return zero.

       The  call  nan("char-sequence")	is  equivalent	to   strtod("NAN(char-
       sequence)",  NULL) and similarly calls to nanf() and nanl() are equiva
       lent to analogous calls to strtof(3) and strtold(3).

       The argument tagp is used in an unspecified manner.  On IEEE  754  sys
       tems,  there are many representations of NaN, and tagp selects one.  On
       other systems it may do nothing.

CONFORMING TO
       C99.  See also IEC 559 and the appendix with recommended  functions  in
       IEEE 754/IEEE 854.

SEE ALSO
       isnan(3), strtod(3), math_error(7)

COLOPHON
       This  page  is  part of release 3.05 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



GNU				  2008-07-23				NAN(3)