логарифмическая гамма-функция (log gamma function)
Имя (Name)
lgamma, lgammaf, lgammal, lgamma_r, lgammaf_r, lgammal_r, signgam
- log gamma function
Синопсис (Synopsis)
#include <math.h>
double lgamma(double x);
float lgammaf(float x);
long double lgammal(long double x);
double lgamma_r(double x, int *signp);
float lgammaf_r(float x, int *signp);
long double lgammal_r(long double x, int *signp);
extern int signgam;
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
lgamma():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
lgammaf(), lgammal():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
lgamma_r(), lgammaf_r(), lgammal_r():
/* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
signgam:
_XOPEN_SOURCE
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
Описание (Description)
For the definition of the Gamma function, see tgamma(3).
The lgamma(), lgammaf(), and lgammal() functions return the
natural logarithm of the absolute value of the Gamma function.
The sign of the Gamma function is returned in the external
integer signgam declared in <math.h>. It is 1 when the Gamma
function is positive or zero, -1 when it is negative.
Since using a constant location signgam is not thread-safe, the
functions lgamma_r(), lgammaf_r(), and lgammal_r() have been
introduced; they return the sign via the argument signp.
Возвращаемое значение (Return value)
On success, these functions return the natural logarithm of
Gamma(x).
If x is a NaN, a NaN is returned.
If x is 1 or 2, +0 is returned.
If x is positive infinity or negative infinity, positive infinity
is returned.
If x is a nonpositive integer, a pole error occurs, and the
functions return +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL,
respectively.
If the result overflows, a range error occurs, and the functions
return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with the
correct mathematical sign.
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:
Pole error: x is a nonpositive integer
errno is set to ERANGE (but see BUGS). A divide-by-zero
floating-point exception (FE_DIVBYZERO) is raised.
Range error: result overflow
errno is set to ERANGE. An overflow floating-point
exception (FE_OVERFLOW) is raised.
Стандарты (Conforming to)
The lgamma() functions are specified in C99, POSIX.1-2001, and
POSIX.1-2008. signgam is specified in POSIX.1-2001 and
POSIX.1-2008, but not in C99. The lgamma_r() functions are
nonstandard, but present on several other systems.
Ошибки (баги) (Bugs)
In glibc 2.9 and earlier, when a pole error occurs, errno is set
to EDOM; instead of the POSIX-mandated ERANGE. Since version
2.10, glibc does the right thing.
Смотри также (See also)
tgamma(3)
