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Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" from: @(#)lgamma.3 6.6 (Berkeley) 12/3/92 29.\" $FreeBSD$ 30.\" 31.Dd September 12, 2014 32.Dt LGAMMA 3 33.Os 34.Sh NAME 35.Nm lgamma , 36.Nm lgamma_r , 37.Nm lgammaf , 38.Nm lgammaf_r , 39.Nm lgammal , 40.Nm lgammal_r , 41.Nm gamma , 42.Nm gamma_r , 43.Nm gammaf , 44.Nm gammaf_r , 45.Nm tgamma , 46.Nm tgammaf 47.Nd log gamma functions, gamma function 48.Sh LIBRARY 49.Lb libm 50.Sh SYNOPSIS 51.In math.h 52.Ft extern int 53.Fa signgam ; 54.sp 55.Ft double 56.Fn lgamma "double x" 57.Ft double 58.Fn lgamma_r "double x" "int *signgamp" 59.Ft float 60.Fn lgammaf "float x" 61.Ft float 62.Fn lgammaf_r "float x" "int *signgamp" 63.Ft "long double" 64.Fn lgammal "long double x" 65.Ft "long double" 66.Fn lgammal_r "long double x" "int *signgamp" 67.Ft double 68.Fn gamma "double x" 69.Ft double 70.Fn gamma_r "double x" "int *signgamp" 71.Ft float 72.Fn gammaf "float x" 73.Ft float 74.Fn gammaf_r "float x" "int *signgamp" 75.Ft "long double" 76.Fn tgamma "double x" 77.Ft float 78.Fn tgammaf "float x" 79.Sh DESCRIPTION 80.Fn lgamma x , 81.Fn lgammaf x , 82and 83.Fn lgammal x 84.if t \{\ 85return ln\||\(*G(x)| where 86.Bd -unfilled -offset indent 87\(*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 88\(*G(x) = \(*p/(\(*G(1\-x)\|sin(\(*px)) for x < 1. 89.Ed 90.\} 91.if n \ 92return ln\||\(*G(x)|. 93The external integer 94.Fa signgam 95returns the sign of \(*G(x). 96.Pp 97.Fn lgamma_r x signgamp , 98.Fn lgammaf_r x signgamp , 99and 100.Fn lgammal_r x signgamp 101provide the same functionality as 102.Fn lgamma x , 103.Fn lgammaf x , 104and 105.Fn lgammal x , 106but the caller must provide an integer to store the sign of \(*G(x). 107.Pp 108The 109.Fn tgamma x 110and 111.Fn tgammaf x 112functions return \(*G(x), with no effect on 113.Fa signgam . 114.Pp 115.Fn gamma , 116.Fn gammaf , 117.Fn gamma_r , 118and 119.Fn gammaf_r 120are deprecated aliases for 121.Fn lgamma , 122.Fn lgammaf , 123.Fn lgamma_r , 124and 125.Fn lgammaf_r , 126respectively. 127 128.Sh IDIOSYNCRASIES 129Do not use the expression 130.Dq Li signgam\(**exp(lgamma(x)) 131to compute g := \(*G(x). 132Instead use a program like this (in C): 133.Bd -literal -offset indent 134lg = lgamma(x); g = signgam\(**exp(lg); 135.Ed 136.Pp 137Only after 138.Fn lgamma 139or 140.Fn lgammaf 141has returned can signgam be correct. 142.Pp 143For arguments in its range, 144.Fn tgamma 145is preferred, as for positive arguments 146it is accurate to within one unit in the last place. 147Exponentiation of 148.Fn lgamma 149will lose up to 10 significant bits. 150.Sh RETURN VALUES 151.Fn gamma , 152.Fn gammaf , 153.Fn gammal , 154.Fn gamma_r , 155.Fn gammaf_r , 156.Fn gammal_r , 157.Fn lgamma , 158.Fn lgammaf , 159.Fn lgammal , 160.Fn lgamma_r , 161.Fn lgammaf_r , 162and 163.Fn lgammal_r 164return appropriate values unless an argument is out of range. 165Overflow will occur for sufficiently large positive values, and 166non-positive integers. 167For large non-integer negative values, 168.Fn tgamma 169will underflow. 170.Sh SEE ALSO 171.Xr math 3 172.Sh STANDARDS 173The 174.Fn lgamma , 175.Fn lgammaf , 176.Fn lgammal , 177.Fn tgamma , 178and 179.Fn tgammaf 180functions are expected to conform to 181.St -isoC-99 . 182.Sh HISTORY 183The 184.Fn lgamma 185function appeared in 186.Bx 4.3 . 187The 188.Fn gamma 189function appeared in 190.Bx 4.4 191as a function which computed \(*G(x). 192This version was used in 193.Fx 1.1 . 194The name 195.Fn gamma 196was originally dedicated to the 197.Fn lgamma 198function, 199and that usage was restored by switching to Sun's fdlibm in 200.Fx 1.1.5 . 201The 202.Fn tgamma 203function appeared in 204.Fx 5.0 . 205