lgamma, lgamma_r, lgammaf, lgammaf_r, gamma, gamma_r, gammaf, gammaf_r,
tgamma -- log gamma functions, gamma function
Math Library (libm, -lm)
extern int signgam;
lgamma_r(double x, int *signgamp);
lgammaf_r(float x, int *signgamp);
gamma_r(double x, int *signgamp);
gammaf_r(float x, int *signgamp);
lgamma(x) and lgammaf(x) return ln|| (x)|.
The external integer signgam returns the sign of | (x).
lgamma_r(x, signgamp) and lgammaf_r(x, signgamp) provide the same functionality
as lgamma(x) and lgammaf(x) but the caller must provide an
integer to store the sign of | (x).
gamma(), gammaf(), gamma_r(), and gammaf_r() are deprecated aliases for
lgamma(), lgammaf()_ lgamma_r(), and lgammaf_r(), respectively.
tgamma(x) returns | (x), with no effect on signgam.
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, tgamma() is preferred, as for positive arguments
it is accurate to within one unit in the last place. Exponentiation
of lgamma() will lose up to 10 significant bits.
gamma(), gamma_r(), gammaf(), gammaf_r(), lgamma(), lgamma_r(),
lgammaf(), and lgammaf_r() return appropriate values unless an argument
is out of range. Overflow will occur for sufficiently large positive
values, and non-positive integers. On the VAX, the reserved operator is
returned, and errno is set to ERANGE. For large non-integer negative
values, tgamma() will underflow.
The lgamma() and tgamma() functions are expected to conform to ISO/IEC
9899:1999 (``ISO C99'').
The lgamma() function appeared in 4.3BSD_ The gamma() function appeared
in 4.4BSD as a function which computed | (x). This version was used in
FreeBSD 1.1. The name gamma() was originally dedicated to the lgamma()
function, and that usage was restored by switching to Sun's fdlibm in
FreeBSD 1.1.5. The tgamma() function appeared in FreeBSD 5.0.
FreeBSD 5.2.1 December 3, 1992 FreeBSD 5.2.1 [ Back ]