nan, nanf, nanl - return 'Not a Number'
#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
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.
These functions first appeared in glibc in version 2.1.
For an explanation of the terms used in this section, see
attributes(7).
| Interface |
Attribute |
Value |
| nan (), nanf (), nanl () |
Thread safety |
MT-Safe locale |
C99, POSIX.1-2001, POSIX.1-2008. See also IEC 559 and the appendix with
recommended functions in IEEE 754/IEEE 854.
isnan(3),
strtod(3),
math_error(7)