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():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

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);

       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  sys-
       tems,  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.

ATTRIBUTES
       For  an  explanation  of  the  terms  used   in   this   section,   see
       attributes(7).

       allbox; lbw21 lb lb l l l.  Interface Attribute Value T{ nan(), nanf(),
       nanl() T}   Thread safety  MT-Safe locale

CONFORMING TO
       C99, POSIX.1-2001, POSIX.1-2008.  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 4.16 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.



GNU                               2016-03-15                            NAN(3)