NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
RETURN VALUE<\/a>
ERRORS<\/a>
EXAMPLES<\/a>
APPLICATION USAGE<\/a>
RATIONALE<\/a>
FUTURE DIRECTIONS<\/a>
SEE ALSO<\/a>
COPYRIGHT<\/a> <\/p>\n
\n
PROLOG <\/a> <\/h2>\nThis manual page is part of the POSIX Programmer\u2019s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.<\/p>\n
![\"Image](\"grohtml-851381.png\")
<\/p>\n
NAME <\/a> <\/h2>\nlgamma, lgammaf, lgammal, signgam \u2014 log gamma function<\/p>\n
SYNOPSIS <\/a> <\/h2>\n#include <\/p>\ndouble lgamma(double x<\/i>);
float lgammaf(float x<\/i>);
long double lgammal(long double x<\/i>);
extern int signgam;<\/p>\nDESCRIPTION <\/a> <\/h2>\nThe functionality described on this reference page is aligned with the ISO\u00a0C standard. Any conflict between the requirements described here and the ISO\u00a0C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO\u00a0C standard.<\/p>\n
These functions shall compute $log_ e” ” \u2502 \u0393 ( ^ x ) \u2502$ where $\u0393 ( ^ x )$ is defined as $int from 0 to inf e”^” ” “{ – t } t”^” ” “{ x – 1 } dt$. The argument x<\/i> need not be a non-positive integer ($\u0393( ^ x )$ is defined over the reals, except the non-positive integers).<\/p>\n
If x<\/i> is NaN, \u2212Inf, or a negative integer, the value of signgam<\/i> is unspecified.<\/p>\n
These functions need not be thread-safe.<\/p>\n
An application wishing to check for error situations should set errno<\/i> to zero and call feclearexcept<\/i>(FE_ALL_EXCEPT) before calling these functions. On return, if errno<\/i> is non-zero or fetestexcept<\/i>(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.<\/p>\nRETURN VALUE <\/a> <\/h2>\nUpon successful completion, these functions shall return the logarithmic gamma of x<\/i>.<\/p>\n
If x<\/i> is a non-positive integer, a pole error shall occur and lgamma<\/i>(), lgammaf<\/i>(), and lgammal<\/i>() shall return +HUGE_VAL, +HUGE_VALF, and +HUGE_VALL, respectively.<\/p>\n
If the correct value would cause overflow, a range error shall occur and lgamma<\/i>(), lgammaf<\/i>(), and lgammal<\/i>() shall return \u00b1HUGE_VAL, \u00b1HUGE_VALF, and \u00b1HUGE_VALL (having the same sign as the correct value), respectively.<\/p>\n
If x<\/i> is NaN, a NaN shall be returned.<\/p>\n
If x<\/i> is 1 or 2, +0 shall be returned.<\/p>\n
If x<\/i> is \u00b1Inf, +Inf shall be returned.<\/p>\nERRORS <\/a> <\/h2>\nThese functions shall fail if:<\/p>\n
<\/p>\nlgamma, lgammaf, lgammal, signgam \u2014 log gamma function<\/p>\n
SYNOPSIS <\/a> <\/h2>\n#include <\/p>\ndouble lgamma(double x<\/i>);
float lgammaf(float x<\/i>);
long double lgammal(long double x<\/i>);
extern int signgam;<\/p>\nDESCRIPTION <\/a> <\/h2>\nThe functionality described on this reference page is aligned with the ISO\u00a0C standard. Any conflict between the requirements described here and the ISO\u00a0C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO\u00a0C standard.<\/p>\n
These functions shall compute $log_ e” ” \u2502 \u0393 ( ^ x ) \u2502$ where $\u0393 ( ^ x )$ is defined as $int from 0 to inf e”^” ” “{ – t } t”^” ” “{ x – 1 } dt$. The argument x<\/i> need not be a non-positive integer ($\u0393( ^ x )$ is defined over the reals, except the non-positive integers).<\/p>\n
If x<\/i> is NaN, \u2212Inf, or a negative integer, the value of signgam<\/i> is unspecified.<\/p>\n
These functions need not be thread-safe.<\/p>\n
An application wishing to check for error situations should set errno<\/i> to zero and call feclearexcept<\/i>(FE_ALL_EXCEPT) before calling these functions. On return, if errno<\/i> is non-zero or fetestexcept<\/i>(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.<\/p>\nRETURN VALUE <\/a> <\/h2>\nUpon successful completion, these functions shall return the logarithmic gamma of x<\/i>.<\/p>\n
If x<\/i> is a non-positive integer, a pole error shall occur and lgamma<\/i>(), lgammaf<\/i>(), and lgammal<\/i>() shall return +HUGE_VAL, +HUGE_VALF, and +HUGE_VALL, respectively.<\/p>\n
If the correct value would cause overflow, a range error shall occur and lgamma<\/i>(), lgammaf<\/i>(), and lgammal<\/i>() shall return \u00b1HUGE_VAL, \u00b1HUGE_VALF, and \u00b1HUGE_VALL (having the same sign as the correct value), respectively.<\/p>\n
If x<\/i> is NaN, a NaN shall be returned.<\/p>\n
If x<\/i> is 1 or 2, +0 shall be returned.<\/p>\n
If x<\/i> is \u00b1Inf, +Inf shall be returned.<\/p>\nERRORS <\/a> <\/h2>\nThese functions shall fail if:<\/p>\n
double lgamma(double x<\/i>); The functionality described on this reference page is aligned with the ISO\u00a0C standard. Any conflict between the requirements described here and the ISO\u00a0C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO\u00a0C standard.<\/p>\n These functions shall compute $log_ e” ” \u2502 \u0393 ( ^ x ) \u2502$ where $\u0393 ( ^ x )$ is defined as $int from 0 to inf e”^” ” “{ – t } t”^” ” “{ x – 1 } dt$. The argument x<\/i> need not be a non-positive integer ($\u0393( ^ x )$ is defined over the reals, except the non-positive integers).<\/p>\n If x<\/i> is NaN, \u2212Inf, or a negative integer, the value of signgam<\/i> is unspecified.<\/p>\n These functions need not be thread-safe.<\/p>\n An application wishing to check for error situations should set errno<\/i> to zero and call feclearexcept<\/i>(FE_ALL_EXCEPT) before calling these functions. On return, if errno<\/i> is non-zero or fetestexcept<\/i>(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.<\/p>\n Upon successful completion, these functions shall return the logarithmic gamma of x<\/i>.<\/p>\n If x<\/i> is a non-positive integer, a pole error shall occur and lgamma<\/i>(), lgammaf<\/i>(), and lgammal<\/i>() shall return +HUGE_VAL, +HUGE_VALF, and +HUGE_VALL, respectively.<\/p>\n If the correct value would cause overflow, a range error shall occur and lgamma<\/i>(), lgammaf<\/i>(), and lgammal<\/i>() shall return \u00b1HUGE_VAL, \u00b1HUGE_VALF, and \u00b1HUGE_VALL (having the same sign as the correct value), respectively.<\/p>\n If x<\/i> is NaN, a NaN shall be returned.<\/p>\n If x<\/i> is 1 or 2, +0 shall be returned.<\/p>\n If x<\/i> is \u00b1Inf, +Inf shall be returned.<\/p>\n These functions shall fail if:<\/p>\n
float lgammaf(float x<\/i>);
long double lgammal(long double x<\/i>);
extern int signgam;<\/p>\nDESCRIPTION <\/a> <\/h2>\n
RETURN VALUE <\/a> <\/h2>\n
ERRORS <\/a> <\/h2>\n