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LGAMMA(3)             DragonFly Library Functions Manual             LGAMMA(3)

NAME
     lgamma, lgammaf, lgammal, lgamma_r, lgammaf_r, tgamma, tgammaf, tgammal
     -- log gamma functions

SYNOPSIS
     #include <math.h>

     extern int signgam;

     double
     lgamma(double x);

     float
     lgammaf(float x);

     long double
     lgammal(long double x);

     double
     lgamma_r(double x, int *signgamp);

     float
     lgammaf_r(float x, int *signgamp);

     double
     tgamma(double x);

     float
     tgammaf(float x);

     long double
     tgammal(long double x);

DESCRIPTION                _
     lgamma(x) returns ln|| (x)|.
                                                       _
     The external integer signgam returns the sign of | (x).  The lgammaf()
     function is a single precision version of lgamma().  The lgammal()
     function is an extended precision version of lgamma().

     The lgamma_r() and lgammaf_r() functions are thread-safe versions of
     lgamma() and lgammaf() that return the sign via the signgamp pointer
     instead of modifying signgam.
                                                                _
     The tgamma(x), tgammaf(x) and tgammal(x) functions return | (x), with no
     effect on signgam.

IDIOSYNCRASIES                                                           _
     Do not use the expression `signgam*exp(lgamma(x))' to compute g := | (x).
     Instead use a program like this (in C):

           lg = lgamma(x); g = signgam*exp(lg);

     Only after lgamma() has returned can signgam be correct.

     For arguments in its range, tgamma() is preferred, as for positive
     arguments it is accurate to within one unit in the last place.

RETURN VALUES
     lgamma() returns appropriate values unless an argument is out of range.
     Overflow will occur for sufficiently large positive values, and non-
     positive integers.  For large non-integer negative values, tgamma() will
     underflow.  On the VAX, the reserved operator is returned, and errno is
     set to ERANGE.

SEE ALSO
     infnan(3)

STANDARDS
     The lgamma(), lgammaf(), lgammal(), tgamma(), tgammaf(), and tgammal()
     functions are expected to conform to ISO/IEC 9899:1999 (``ISO C99'').

     The lgamma_r() and lgammaf_r() functions are BSD extensions.

     gamma() and gammaf() are deprecated aliases for lgamma() and lgammaf(),
     respectively.

HISTORY
     A gamma() function first appeared in Version 5 AT&T UNIX.  The lgamma()
     function first appeared in 4.3BSD.  The tgamma() function first appeared
     in OpenBSD 4.4, and is based on t_e gamma() function that appeared in
     4.4BSD as a function to compute | (x).

DragonFly 4.3                  January 15, 2015                  DragonFly 4.3