nan(3) — Linux manual page


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

NAME         top

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

SYNOPSIS         top

       #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

       nan(), nanf(), nanl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION         top

       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         top

       These functions first appeared in glibc in version 2.1.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface                      Attribute     Value          │
       │nan(), nanf(), nanl()          │ Thread safety │ MT-Safe locale │

CONFORMING TO         top

       C99, POSIX.1-2001, POSIX.1-2008.  See also IEC 559 and the
       appendix with recommended functions in IEEE 754/IEEE 854.

SEE ALSO         top

       isnan(3), strtod(3), math_error(7)

COLOPHON         top

       This page is part of release 5.13 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

GNU                            2021-03-22                         NAN(3)

Pages that refer to this page: strtod(3)math_error(7)