NAME | SYNOPSIS | DESCRIPTION | VERSIONS | CONFORMING TO | SEE ALSO | COLOPHON

The Linux Programming Interface

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 feature_test_macros(7)):

       nan(), nanf(), nanl():
           _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

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.

CONFORMING TO         top

       C99, POSIX.1-2001.  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 3.32 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/.

GNU                                   2010-09-20                               NAN(3)

HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface