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TGAMMA(3)                BSD Library Functions Manual                TGAMMA(3)

NAME
     tgamma, lgamma, gamma -- gamma and log of gamma

SYNOPSIS
     #include <math.h>

     double
     tgamma(double x);

     long double
     tgammal(long double x);

     float
     tgammaf(float x);

     double
     lgamma(double x);

     long double
     lgammal(long double x);

     float
     lgammaf(float x);

     double
     gamma(double x);

DESCRIPTION
     tgamma() calculates the gamma function of x.  lgamma() calculates the natural logorithm of the absolute
     value of the gamma function of x.  gamma() is the same function as tgamma. Its use is deprecated.

SPECIAL VALUES
     tgamma(+-0) returns +-infinity and raises the "divide-by-zero" floating-point exception.

     tgamma(x) returns a NaN and raises the "invalid" floating-point exception if x is a negative integer.

     tgamma(-infinity) returns a NaN and raises the "invalid" floating-point exception.

     tgamma(+infinity) returns +infinity.

     tgamma(x) generates a domain error if x is a negative integer or if the result cannnot be respresented
     when x is 0.

     A range error may occur if the magnitude of x is too large or too small.

     gamma() has the same behavior as tgamma().

     lgamma(1) returns +0.

     lgamma(2) returns +0.

     lgamma(x) returns +infinity and raises the "divide-by-zero" floating-point exception if x is a negative
     integer or 0.

     lgamma(+-infinity) returns +infinity.

     lgamma(x) generates a range error if x is too large.

     A range error may occur if x is a negative integer or 0.

NOTE
     lgamma(x) and its variants have the (non-threadsafe) side-effect of setting the global variable signgam
     to +-1, equal to the sign of tgamma(x).

SEE ALSO
     math(3)

STANDARDS
     The tgamma() , and lgamma() functions conform to ISO/IEC 9899:1999(E).

                                  Oct 9, 2006