lgammaf man page on BSDi

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LGAMMA(3)		    BSD Programmer's Manual		     LGAMMA(3)

NAME
     lgamma, lgammaf, gamma, gammaf, lgamma_r, lgammaf_r, gamma_r, gammaf_r -
     log gamma functions, gamma functions

SYNOPSIS
     #include <math.h>

     extern int signgam;

     double
     lgamma(double x);

     float
     lgammaf(float x);

     double
     gamma(double x);

     float
     gammaf(float x);

     double
     lgamma_r(double x, int *sign);

     float
     lgammaf_r(float x, int *sign);

     double
     gamma_r(double x, int *sign);

     float
     gammaf_r(float x, int *sign);

DESCRIPTION				 _
     lgamma(x) and lgammaf(x) return ln|| (x)|.
						       _
     The external integer signgam returns the sign of | (x).
				    _
     gamma(x) and gammaf(x) return | (x), with no effect on signgam.

     The functions lgamma_r(), lgammaf_r(), gamma_r() and gammaf_r() are iden-
     tical to the versions without the _r suffixes, but instead of setting the
     global variable signgam, they store the sign indirectly through their
     sign argument.  This avoids any races between asynchronous threads to set
     a global variable like signgam.

IDIOSYNCRASIES
     D_ 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() or lgammaf() has returned can signgam be correct.

     For arguments in its range, gamma() and gammaf() is preferred, as for
     positive arguments it can be more accurate.  Exponentiation of lgamma()
     may lose several significant bits.

ERRORS
     If the result would overflow, then:

     _IEEE_    The return value is +Inf.
     _POSIX_   Same as _IEEE_, but errno is also set to ERANGE.
     _XOPEN_   Same as _POSIX_, but errno is only set if matherr(3) returns 0.
	       The exception type is OVERFLOW.
     _SVID_    Same as _XOPEN_, but the return value is MAXFLOAT.

     If x is a nonpositive integer value, then:

     _IEEE_    The return value is +Inf.
     _POSIX_   Same as _IEEE_, but errno is also set to EDOM.
     _XOPEN_   Same as _POSIX_, but errno is only set if matherr(3) returns 0.
	       The exception type is SING.
     _SVID_    Same as _XOPEN_, but the return value is MAXFLOAT, and a mes-
	       sage is printed to stderr if errno is set.

SEE ALSO
     math(3)

HISTORY
     The lgamma function appeared in 4.3BSD. The gamma function appeared in
     4.4BSD. The name gamma() was originally dedicated to the lgamma() func-
     tion, so some old code may no longer be compatible.

4.3 Berkeley Distribution      February 17, 1998			     2
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