diff options
Diffstat (limited to 'missing')
| -rw-r--r-- | missing/tgamma.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/missing/tgamma.c b/missing/tgamma.c index a30108e0b..4ace1bcc5 100644 --- a/missing/tgamma.c +++ b/missing/tgamma.c @@ -10,6 +10,7 @@ reference - Haruhiko Okumura: C-gengo niyoru saishin algorithm jiten gamma.c -- Gamma function ***********************************************************/ #include <math.h> +#include <errno.h> #define PI 3.14159265358979324 /* $\pi$ */ #define LOG_2PI 1.83787706640934548 /* $\log 2\pi$ */ #define N 8 @@ -42,8 +43,22 @@ loggamma(double x) /* the natural logarithm of the Gamma function. */ double tgamma(double x) /* Gamma function */ { - if (x < 0) - return PI / (sin(PI * x) * exp(loggamma(1 - x))); + 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)); } |