NAN
Section: Linux Programmer's Manual (3)
Updated: 2016-03-15
Page Index
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
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