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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 3.54 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/.