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Diffstat (limited to 'trunk/missing/tgamma.c')
-rw-r--r-- | trunk/missing/tgamma.c | 92 |
1 files changed, 0 insertions, 92 deletions
diff --git a/trunk/missing/tgamma.c b/trunk/missing/tgamma.c deleted file mode 100644 index 5e306fbb43..0000000000 --- a/trunk/missing/tgamma.c +++ /dev/null @@ -1,92 +0,0 @@ -/* tgamma.c - public domain implementation of function tgamma(3m) - -reference - Haruhiko Okumura: C-gengo niyoru saishin algorithm jiten - (New Algorithm handbook in C language) (Gijyutsu hyouron - sha, Tokyo, 1991) [in Japanese] - http://oku.edu.mie-u.ac.jp/~okumura/algo/ -*/ - -/*********************************************************** - gamma.c -- Gamma function -***********************************************************/ -#include "ruby/config.h" -#include <math.h> -#include <errno.h> - -#ifdef HAVE_LGAMMA_R - -double tgamma(double x) -{ - int sign; - double d; - if (x == 0.0) { /* Pole Error */ - errno = ERANGE; - return 1/x < 0 ? -HUGE_VAL : HUGE_VAL; - } - if (x < 0) { - static double zero = 0.0; - double i, f; - f = modf(-x, &i); - if (f == 0.0) { /* Domain Error */ - errno = EDOM; - return zero/zero; - } - } - d = lgamma_r(x, &sign); - return sign * exp(d); -} - -#else - -#include <errno.h> -#define PI 3.14159265358979324 /* $\pi$ */ -#define LOG_2PI 1.83787706640934548 /* $\log 2\pi$ */ -#define N 8 - -#define B0 1 /* Bernoulli numbers */ -#define B1 (-1.0 / 2.0) -#define B2 ( 1.0 / 6.0) -#define B4 (-1.0 / 30.0) -#define B6 ( 1.0 / 42.0) -#define B8 (-1.0 / 30.0) -#define B10 ( 5.0 / 66.0) -#define B12 (-691.0 / 2730.0) -#define B14 ( 7.0 / 6.0) -#define B16 (-3617.0 / 510.0) - -static double -loggamma(double x) /* the natural logarithm of the Gamma function. */ -{ - double v, w; - - v = 1; - while (x < N) { v *= x; x++; } - w = 1 / (x * x); - return ((((((((B16 / (16 * 15)) * w + (B14 / (14 * 13))) * w - + (B12 / (12 * 11))) * w + (B10 / (10 * 9))) * w - + (B8 / ( 8 * 7))) * w + (B6 / ( 6 * 5))) * w - + (B4 / ( 4 * 3))) * w + (B2 / ( 2 * 1))) / x - + 0.5 * LOG_2PI - log(v) - x + (x - 0.5) * log(x); -} - -double tgamma(double x) /* Gamma function */ -{ - if (x == 0.0) { /* Pole Error */ - errno = ERANGE; - return 1/x < 0 ? -HUGE_VAL : HUGE_VAL; - } - if (x < 0) { - int sign; - static double zero = 0.0; - double i, f; - f = modf(-x, &i); - if (f == 0.0) { /* Domain Error */ - errno = EDOM; - return zero/zero; - } - sign = (fmod(i, 2.0) != 0.0) ? 1 : -1; - return sign * PI / (sin(PI * f) * exp(loggamma(1 - x))); - } - return exp(loggamma(x)); -} -#endif |