tgamma.3   [plain text]


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.\"     from: @(#)erf.3	6.4 (Berkeley) 4/20/91
.\"	$Id: tgamma.3,v 1.4 2004/12/20 21:35:46 scp Exp $
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.Dd July 23, 2003
.Dt TGAMMA 3
.Sh NAME
.Nm tgamma ,
.Nm lgamma ,
.Nm gamma
.Nd gamma and log of gamma
.Sh SYNOPSIS
.Fd #include <math.h>
.Ft double
.Fn tgamma "double x"
.Ft long double
.Fn tgammal "long double x"
.Ft float
.Fn tgamma "float x"
.Ft double
.Fn lgamma "double x"
.Ft float
.Fn lgamma "float x"
.Ft double
.Fn gamma "double x"
.Sh DESCRIPTION
.Fn tgamma
calculates the gamma function of x.
.Fn lgamma
calculates the natural logorithm of the absolute value of the gamma function of x.
.Fn gamma
is the same function as tgamma. Its use is deprecated. 
.Sh SPECIAL VALUES
.Fn tgamma "±0"
returns ±infinity and raises the "divide-by-zero" floating-point exception.
.Pp
.Fn tgamma "x"
returns a NaN and raises the "invalid" floating-point exception if x is a negative integer. 
.Pp
.Fn tgamma "-infinity"
returns a NaN and raises the "invalid" floating-point exception.
.Pp
.Fn tgamma "+infinity"
returns +infinity.
.Pp
.Fn tgamma "x"
generates a domain error if x is a negative integer or if the result cannnot be respresented when x is 0.
.Pp
A range error may occur if the magnitude of x is too large or too small.
.Pp
.Fn gamma
has the same behavior as
.Fn tgamma
.Pp
.Fn lgamma "1"
returns +0.
.Pp
.Fn lgamma "2"
returns +0.
.Pp
.Fn lgamma "x"
returns +infinity and raises the "divide-by-zero" floating-point exception if x is a negative integer or 0.
.Pp
.Fn lgamma "±infinity"
returns +infinity.
.Pp
.Fn lgamma "x"
generates a range error if x is too large.
.Pp
A range error may occur if x is a negative integer or 0.
.Sh SEE ALSO
.Xr math 3
.Sh STANDARDS
The
.Fn tgamma
, and
.Fn lgamma
functions conform to ISO/IEC 9899:1999(E).