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28 .\" from: @(#)lgamma.3 6.6 (Berkeley) 12/3/92
48 .Nd log gamma functions, gamma function
59 .Fn lgamma_r "double x" "int *signgamp"
63 .Fn lgammaf_r "float x" "int *signgamp"
65 .Fn lgammal "long double x"
67 .Fn lgammal_r "long double x" "int *signgamp"
71 .Fn gamma_r "double x" "int *signgamp"
75 .Fn gammaf_r "float x" "int *signgamp"
81 .Fn tgammal "long double x"
88 return ln\||\(*G(x)| where
89 .Bd -unfilled -offset indent
90 \(*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
91 \(*G(x) = \(*p/(\(*G(1\-x)\|sin(\(*px)) for x < 1.
98 returns the sign of \(*G(x).
100 .Fn lgamma_r x signgamp ,
101 .Fn lgammaf_r x signgamp ,
103 .Fn lgammal_r x signgamp
104 provide the same functionality as
109 but the caller must provide an integer to store the sign of \(*G(x).
116 functions return \(*G(x), with no effect on
124 are deprecated aliases for
133 Do not use the expression
134 .Dq Li signgam\(**exp(lgamma(x))
135 to compute g := \(*G(x).
136 Instead use a program like this (in C):
137 .Bd -literal -offset indent
138 lg = lgamma(x); g = signgam\(**exp(lg);
145 has returned can signgam be correct.
147 For arguments in its range,
149 is preferred, as for positive arguments
150 it is accurate to within one unit in the last place.
153 will lose up to 10 significant bits.
168 return appropriate values unless an argument is out of range.
169 Overflow will occur for sufficiently large positive values, and
170 non-positive integers.
171 For large non-integer negative values,
175 To conform with newer C/C++ standards, a stub implementation for
177 was committed to the math library, where
181 Thus, the numerical accuracy is at most that of the 53-bit double
182 precision implementation.
194 functions are expected to conform to
205 as a function which computed \(*G(x).
206 This version was used in
210 was originally dedicated to the
213 and that usage was restored by switching to Sun's fdlibm in