mirror of https://github.com/mkerrisk/man-pages
67 lines
1.7 KiB
Groff
67 lines
1.7 KiB
Groff
.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
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.\" Distributed under GPL
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.\"
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.\" Modified 2003-11-18, aeb: historical remarks
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.\"
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.TH GAMMA 3 2002-08-10 "GNU" "libc math functions"
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.SH NAME
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gamma, gammaf, gammal \- (logarithm of the) gamma function
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.SH SYNOPSIS
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.B #include <math.h>
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.sp
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.BI "double gamma(double " x ");"
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.br
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.BI "float gammaf(float " x ");"
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.br
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.BI "long double gammal(long double " x ");"
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.sp
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Link with \-lm.
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.SH DESCRIPTION
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For the definition of the Gamma function, see
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.BR tgamma (3).
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.SS "*BSD version"
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4.4BSD and FreeBSD libm have a
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.BR gamma ()
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function that computes the Gamma function, as one would expect.
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.SS "glibc version"
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Glibc has a
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.BR gamma ()
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function that is equivalent to
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.BR lgamma ()
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and computes the natural logarithm of the Gamma function.
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(This is for compatibility reasons only. Don't use this function.)
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.SH HISTORY
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4.2BSD had a
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.BR gamma ()
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that computed
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.RI ln(|Gamma(| x |)|),
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leaving the sign of
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.RI Gamma(| x |)
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in the external integer
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.IR signgam .
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In 4.3BSD the name was changed to
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.BR lgamma (),
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and the man page promises
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.sp
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.in +3
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"At some time in the future the name gamma will be rehabilitated
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and used for the Gamma function"
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.in
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.sp
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This did indeed happen in 4.4BSD, where
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.BR gamma ()
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computes the Gamma function (with no effect on
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.IR signgam ).
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However, this came too late, and we now have
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.BR tgamma (),
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the "true gamma" function.
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.\" The FreeBSD man page says about gamma() that it is like lgamma()
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.\" except that is does not set signgam.
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.\" Also, that 4.4BSD has a gamma() that computes the true gamma function.
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.SH "CONFORMING TO"
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4.2BSD. Compatible with previous mistakes.
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.SH "SEE ALSO"
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.BR lgamma (3),
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.BR signgam (3),
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.BR tgamma (3)
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