nan(3) - Linux manual page (original) (raw)

nan(3) Library Functions Manual nan(3)

NAME top

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

LIBRARY top

   Math library (_libm_, _-lm_)

SYNOPSIS top

   **#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 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)](../man3/strtof.3.html) and [strtold(3)](../man3/strtold.3.html).

   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 top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌───────────────────────────────┬───────────────┬────────────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├───────────────────────────────┼───────────────┼────────────────┤
   │ **nan**(), **nanf**(), **nanl**()         │ Thread safety │ MT-Safe locale │
   └───────────────────────────────┴───────────────┴────────────────┘

STANDARDS top

   C11, POSIX.1-2008.

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

HISTORY top

   glibc 2.1.  C99, POSIX.1-2001.

SEE ALSO top

   [isnan(3)](../man3/isnan.3.html), [strtod(3)](../man3/strtod.3.html), [math_error(7)](../man7/math%5Ferror.7.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 nan(3)

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