From fc94b49ada9a4d522bdd620d2dc2a54e450bbbab Mon Sep 17 00:00:00 2001
From: Dongryeol Lee <drselee@gmail.com>
Date: Thu, 14 Aug 2008 17:55:22 +0000
Subject: [PATCH] Bug fix for math::BinomialCoefficient(n, k); the previous
 implementation returned 1 for negative k values, which is not correct (should
 be zero.

---
 fastlib2/fastlib/math/discrete.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fastlib2/fastlib/math/discrete.cc b/fastlib2/fastlib/math/discrete.cc
index a9ea1121f7..cfeed86175 100644
--- a/fastlib2/fastlib/math/discrete.cc
+++ b/fastlib2/fastlib/math/discrete.cc
@@ -15,8 +15,9 @@ double math::BinomialCoefficient(int n, int k) {
   double nchsk = 1;
   int i;
   
-  if(k > n)
+  if(k > n || k < 0) {
     return 0;
+  }
   
   if(k < n_k) {
     k = n_k;