lgamma, lgammaf, lgammal, gamma, signgam - compute logarithm of gamma function

Definition	#include <math.h> double gamma(double x); double lgamma(double x); float lgammaf(float x); (C11) long double lgammal(long double x); (C11) extern int signgam; These functions compute the natural logarithm of the absolute value of the mathematical gamma function for a given floating-point number x: The sign of this value is stored as +1 or -1 in the internal C variable signgam. The signgam variable must not be defined by the user.
Return val.	log(|tgamma(x)|)	if successful.
	HUGE_VAL HUGE_VALF HUGE_VALL	depending on the function type, if the correct value results in an overflow. In addition, errno is set to ERANGE (result too large).
	HUGE_VAL HUGE_VALF HUGE_VALL	depending on the function type, if x is a non-positive integer. In addition, errno is set to EDOM (illegal argument).
See also	fabs, tgamma