вернуть 'Not a Number' (return 'Not a Number')
Имя (Name)
nan, nanf, nanl - return 'Not a Number'
Синопсис (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
Описание (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.
Версии (Versions)
These functions first appeared in glibc in version 2.1.
Атрибуты (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 │
└───────────────────────────────┴───────────────┴────────────────┘
Стандарты (Conforming to)
C99, POSIX.1-2001, POSIX.1-2008. See also IEC 559 and the
appendix with recommended functions in IEEE 754/IEEE 854.
Смотри также (See also)
isnan(3), strtod(3), math_error(7)
