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28 .\" from: @(#)lgamma.3 6.6 (Berkeley) 12/3/92
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45 .Nd log gamma functions, gamma function
56 .Fn lgamma_r "double x" "int *signgamp"
60 .Fn lgammaf_r "float x" "int *signgamp"
64 .Fn gamma_r "double x" "int *signgamp"
68 .Fn gammaf_r "float x" "int *signgamp"
78 return ln\||\(*G(x)| where
79 .Bd -unfilled -offset indent
80 \(*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
81 \(*G(x) = \(*p/(\(*G(1\-x)\|sin(\(*px)) for x < 1.
88 returns the sign of \(*G(x).
90 .Fn lgamma_r x signgamp
92 .Fn lgammaf_r x signgamp
93 provide the same functionality as
97 but the caller must provide an integer to store the sign of \(*G(x).
103 functions return \(*G(x), with no effect on
111 are deprecated aliases for
119 Do not use the expression
120 .Dq Li signgam\(**exp(lgamma(x))
121 to compute g := \(*G(x).
122 Instead use a program like this (in C):
123 .Bd -literal -offset indent
124 lg = lgamma(x); g = signgam\(**exp(lg);
131 has returned can signgam be correct.
133 For arguments in its range,
135 is preferred, as for positive arguments
136 it is accurate to within one unit in the last place.
139 will lose up to 10 significant bits.
150 return appropriate values unless an argument is out of range.
151 Overflow will occur for sufficiently large positive values, and
152 non-positive integers.
153 For large non-integer negative values,
165 functions are expected to conform to
176 as a function which computed \(*G(x).
177 This version was used in
181 was originally dedicated to the
184 and that usage was restored by switching to Sun's fdlibm in