gamma.3

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.th GAMMA III 5/15/74
.sh NAME
gamma \*- log gamma function
.sh SYNOPSIS
.br
.ft B
jsr	pc,gamma
.s3
double gamma(x)
.br
double x;
.ft R
.sh DESCRIPTION
If \fIx\fR is passed (in fr0)
.it gamma
returns
ln |\*|\*G(\*|\fIx\fR\*|)\*|| (in fr0).
The sign of
\*G(\*|\fIx\fR\*|)
is returned in the external integer
.it signgam.
The following C program might be
used to calculate
\*G:
.s3
	y = gamma(x);
.br
	if (y > 88.)
.br
		error( );
.br
	y = exp(y);
.br
	if(signgam)
.br
		y = \*-y;
.sh DIAGNOSTICS
The c-bit is
set on negative integral arguments and the
maximum value is returned.
There is no error return for C programs.
.sh BUGS
No error return from C.