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lgamma(3) Library Functions Manual lgamma(3) NAME lgamma, gamma - Compute the logarithm of the gamma function LIBRARY Math Library (libm.a) SYNOPSIS #include <math.h> double lgamma (double x); float lgammaf (float x); STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: lgamma(): XPG4 gamma(): XPG4 Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. DESCRIPTION The lgamma() and lgammaf() functions return the logarithm of the ab- solute value of gamma of x, or ln(|G(x)|), where G is the gamma func- tion. The sign of gamma of x is returned in the external integer vari- able signgam. The x parameter cannot be 0 or a negative integer. The gamma() function returns the natural log of the gamma function and so is functionally equivalent to lgamma(). Because of this, gamma() is marked TO BE WITHDRAWN in the X/Open Portability Guide, Revision 4 (XPG4). The following table describes function behavior in response to excep- tional arguments: tab(@); lfHB lfHB lfHB l l l . _ Function@Exceptional Argument@Routine Behavior _ lgamma(), lgammaf()@|x| = infinity@Invalid argument lgamma(), lgam- maf()@x = 0, -1, -2, -3,...@Invalid argument lgamma(), lgammaf()@x > lgamma_max_float@Overflow _ The following table lists boundary values used by these functions: tab(@); lfHB lfHB lfHB lfHB lfHB lfHB lfHB lfHB l l l l. _ Value@Data@Hexadecimal Value@Decimal Value Name@Type _ lgamma_max_float@S_FLOAT @7BC650F9 @2.0594342e36 @T_FLOAT @7F475ABDC501F55F @1.2812545499066958e305 _ delim off lgamma(3)