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
       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.

ATTRIBUTES

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

       +----------------------+---------------+----------------+
       |Interface	      | Attribute     | Value	       |
       +----------------------+---------------+----------------+
       |nan(), nanf(), nanl() | 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 4.15 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)