1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
140 lines
3.7 KiB
Groff
140 lines
3.7 KiB
Groff
.\" Copyright (c) 1985, 1991 Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" from: @(#)lgamma.3 6.6 (Berkeley) 12/3/92
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.\" $FreeBSD$
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.\"
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.Dd December 3, 1992
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.Dt LGAMMA 3
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.Os BSD 4.3
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.Sh NAME
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.Nm lgamma ,
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.Nm lgammaf ,
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.Nm gamma ,
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.Nm gammaf
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.Nd log gamma functions, gamma functions
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.Sh SYNOPSIS
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.Fd #include <math.h>
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.Ft extern int
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.Fa signgam ;
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.sp
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.Ft double
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.Fn lgamma "double x"
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.Ft float
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.Fn lgammaf "float x"
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.Ft double
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.Fn gamma "double x"
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.Ft float
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.Fn gamma "float x"
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.Sh DESCRIPTION
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.Fn lgamma x
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and
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.Fn lgammaf x
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.if t \{\
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return ln\||\(*G(x)| where
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.Bd -unfilled -offset indent
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\(*G(x) = \(is\d\s8\z0\s10\u\u\s8\(if\s10\d t\u\s8x\-1\s10\d e\u\s8\-t\s10\d dt for x > 0 and
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.br
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\(*G(x) = \(*p/(\(*G(1\-x)\|sin(\(*px)) for x < 1.
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.Ed
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.\}
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.if n \
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returns ln\||\(*G(x)|.
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.Pp
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The external integer
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.Fa signgam
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returns the sign of \(*G(x).
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.Pp
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.Fn gamma x
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and
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.Fn gammaf x
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return \(*G(x), with no effect on
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.Fa signgam .
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.Sh IDIOSYNCRASIES
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Do not use the expression
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.Dq Li signgam\(**exp(lgamma(x))
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to compute g := \(*G(x).
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Instead use a program like this (in C):
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.Bd -literal -offset indent
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lg = lgamma(x); g = signgam\(**exp(lg);
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.Ed
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.Pp
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Only after
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.Fn lgamma
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or
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.Fn lgammaf
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has returned can signgam be correct.
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.Pp
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For arguments in its range,
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.Fn gamma
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and
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.Fn gammaf
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is preferred, as for positive arguments
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it is accurate to within one unit in the last place.
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Exponentiation of
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.Fn lgamma
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will lose up to 10 significant bits.
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.Sh RETURN VALUES
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.Fn gamma ,
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.Fn gammaf ,
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.Fn lgamma ,
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and
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.Fn lgammaf
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return appropriate values unless an argument is out of range.
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Overflow will occur for sufficiently large positive values, and
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non-positive integers.
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On the
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.Tn VAX,
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the reserved operator is returned,
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and
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.Va errno
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is set to
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.Er ERANGE
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For large non-integer negative values,
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.Fn gamma
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will underflow.
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.Sh SEE ALSO
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.Xr math 3
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.Sh HISTORY
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The
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.Nm lgamma
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function appeared in
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.Bx 4.3 .
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The
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.Nm gamma
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function appeared in
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.Bx 4.4 .
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The name
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.Fn gamma
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was originally dedicated to the
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.Fn lgamma
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function, so some old code may no longer be compatible.
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