Hello,
Since the 2F1 series is finite for either a or b being negative, this
should be used irrespectively of whether the absolute values are below
10.0 (why this specific value, BTW?).
The patch is attached.
Regards,
Evgeny
--- hyperg_2F1.c.orig 2004-06-20 21:41:17.000000000 +0300
+++ hyperg_2F1.c 2005-07-12 17:56:47.000000000 +0300
@@ -656,17 +656,18 @@ gsl_sf_hyperg_2F1_e(double a, double b,
return hyperg_2F1_series(a, b, c, x, result);
}
+ /* Negative a or b result in finite series. */
+ if(a_neg_integer) {
+ return hyperg_2F1_series(rinta, b, c, x, result);
+ }
+ if(b_neg_integer) {
+ return hyperg_2F1_series(a, rintb, c, x, result);
+ }
+
if(fabs(a) < 10.0 && fabs(b) < 10.0) {
/* a and b are not too large, so we attempt
* variations on the series summation.
*/
- if(a_neg_integer) {
- return hyperg_2F1_series(rinta, b, c, x, result);
- }
- if(b_neg_integer) {
- return hyperg_2F1_series(a, rintb, c, x, result);
- }
-
if(x < -0.25) {
return hyperg_2F1_luke(a, b, c, x, result);
}
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