From a38e25ac8202829a48ba4d9e899c4297ee51d0b7 Mon Sep 17 00:00:00 2001 From: "Vladimir V. Kisil" Date: Tue, 7 Feb 2023 22:34:55 +0000 Subject: [PATCH 2/2] Extend applicability of binomial evaluation. When binomial(n,k) has both n<0 and k<0 but n-k>=0 we can use the symmetry relation binomial(n,k) = binomial(n, n-k). Suggested by Marko Riedel . Signed-off-by: Vladimir V. Kisil --- ginac/numeric.cpp | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/ginac/numeric.cpp b/ginac/numeric.cpp index c643d041..98524c51 100644 --- a/ginac/numeric.cpp +++ b/ginac/numeric.cpp @@ -2149,7 +2149,10 @@ const numeric binomial(const numeric &n, const numeric &k) else return *_num0_p; } else { - return _num_1_p->power(k)*binomial(k-n-(*_num1_p),k); + numeric k1 = k; + if ( (not k.is_nonneg_integer()) && (n-k).is_nonneg_integer()) + k1 = n-k; + return _num_1_p->power(k1)*binomial(k1-n-(*_num1_p),k1); } } -- 2.39.1