nan

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 5.04 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)