NAN(3)                              Linux Programmer's Manual                              NAN(3)



NAME
       nan, nanf, nanl - return 'Not a Number'

SYNOPSIS
       #include <math.h>

       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 || _POSIX_C_SOURCE >= 200112L;
           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 functions return zero.

       The call nan("char-sequence") is equivalent to:

           strtod("NAN(char-sequence)", NULL);

       Similarly, calls to nanf() and nanl() are equivalent to analogous calls to  strtof(3)  and
       strtold(3).

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

VERSIONS
       These functions first appeared in glibc in version 2.1.

CONFORMING TO
       C99, POSIX.1-2001.  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 3.53 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                                         2010-09-20                                     NAN(3)