nan(3) — Linux manual page

nan(3)                  Library Functions Manual                  nan(3)

NAME

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

LIBRARY

       Math library (libm, -lm)

SYNOPSIS

       #include <math.h>

       double nan(const char *tagp);
       float nanf(const char *tagp);
       long double nanl(const char *tagp);

   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.

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 │
       └──────────────────────────────┴───────────────┴────────────────┘

STANDARDS

       C11, POSIX.1-2008.

       See also IEC 559 and the appendix with recommended functions in
       IEEE 754/IEEE 854.

HISTORY

       glibc 2.1.  C99, POSIX.1-2001.

SEE ALSO

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

COLOPHON

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Linux man-pages 6.9.1          2024-05-02                         nan(3)

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

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