* missing/tgamma.c (tgamma): use lgamma_r if available.

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@15420 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 30 insertions, 1 deletions

diff --git a/missing/tgamma.c b/missing/tgamma.c
index 4ace1bcc5..91f83fcb8 100644
--- a/missing/tgamma.c
+++ b/missing/tgamma.c
@@ -11,6 +11,35 @@ reference - Haruhiko Okumura: C-gengo niyoru saishin algorithm jiten
 ***********************************************************/
 #include <math.h>
 #include <errno.h>
+#include "ruby/config.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) {
+        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;
+        }
+    }
+    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
@@ -61,4 +90,4 @@ double tgamma(double x)  /* Gamma function */
     }
     return exp(loggamma(x));
 }
-
+#endif