логарифм 1 плюс аргумент (logarithm of 1 plus argument)
Имя (Name)
log1p, log1pf, log1pl - logarithm of 1 plus argument
Синопсис (Synopsis)
#include <math.h>
double log1p(double x);
float log1pf(float x);
long double log1pl(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
log1p():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
log1pf(), log1pl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
Описание (Description)
These functions return a value equivalent to
log (1 + x)
The result is computed in a way that is accurate even if the
value of x is near zero.
Возвращаемое значение (Return value)
On success, these functions return the natural logarithm of
(1 + x).
If x is a NaN, a NaN is returned.
If x is positive infinity, positive infinity is returned.
If x is -1, a pole error occurs, and the functions return
-HUGE_VAL, -HUGE_VALF, or -HUGE_VALL, respectively.
If x is less than -1 (including negative infinity), a domain
error occurs, and a NaN (not a number) is returned.
Ошибки (Error)
See math_error(7) for information on how to determine whether an
error has occurred when calling these functions.
The following errors can occur:
Domain error: x is less than -1
errno is set to EDOM (but see BUGS). An invalid floating-
point exception (FE_INVALID) is raised.
Pole error: x is -1
errno is set to ERANGE (but see BUGS). A divide-by-zero
floating-point exception (FE_DIVBYZERO) is raised.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│log1p(), log1pf(), log1pl() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
C99, POSIX.1-2001, POSIX.1-2008.
Ошибки (баги) (Bugs)
Before version 2.22, the glibc implementation did not set errno
to EDOM when a domain error occurred.
Before version 2.22, the glibc implementation did not set errno
to ERANGE when a range error occurred.
Смотри также (See also)
exp(3), expm1(3), log(3)
