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LGAMMA(3) Linux Programmer's Manual LGAMMA(3)NAMElgamma, lgammaf, lgammal, lgamma_r, lgammaf_r, lgammal_r, signgam - log gamma functionSYNOPSIS#include<math.h>doublelgamma(doublex);floatlgammaf(floatx);longdoublelgammal(longdoublex);doublelgamma_r(doublex,int*signp);floatlgammaf_r(floatx,int*signp);longdoublelgammal_r(longdoublex,int*signp);externintsigngam;Link with-lm. Feature Test Macro Requirements for glibc (see feature_test_macros(7)):lgamma(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; orcc-std=c99lgammaf(),lgammal(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; orcc-std=c99lgamma_r(),lgammaf_r(),lgammal_r(): _BSD_SOURCE || _SVID_SOURCEsigngam: _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCEDESCRIPTIONFor the definition of the Gamma function, see tgamma(3). Thelgamma() function returns the natural logarithm of the absolute value of the Gamma function. The sign of the Gamma function is returned in the external integersigngamdeclared in<math.h>. It is 1 when the Gamma function is positive or zero, -1 when it is negative. Since using a constant locationsigngamis not thread-safe, the functionslgamma_r() etc. have been introduced; they return the sign via the argumentsignp.RETURNVALUEOn success, these functions return the natural logarithm of Gamma(x). Ifxis a NaN, a NaN is returned. Ifxis 1 or 2, +0 is returned. Ifxis positive infinity or negative infinity, positive infinity is returned. Ifxis a non-positive 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 returnHUGE_VAL,HUGE_VALF, orHUGE_VALL, respectively, with the correct mathematical sign.ERRORSSee math_error(7) for information on how to determine whether an error has occurred when calling these func- tions. The following errors can occur: Pole error:xis a non-positive integererrnois set toERANGE(but see BUGS). A divide-by-zero floating-point exception (FE_DIVBYZERO) is raised. Range error: result overflowerrnois set toERANGE. An overflow floating-point exception (FE_OVERFLOW) is raised.CONFORMINGTOThelgamma() functions are specified in C99 and POSIX.1-2001.signgamis specified in POSIX.1-2001, but not in C99. Thelgamma_r() functions are non-standard, but present on several other systems.BUGSFor a pole error,errnois set toEDOM; POSIX.1 says it should be set toERANGE.SEEALSOtgamma(3)COLOPHONThis page is part of release 3.22 of the Linuxman-pagesproject. A description of the project, and informa- tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2008-08-05 LGAMMA(3)