From deb4de90a25928ff59985e12f5006dc172708dbf Mon Sep 17 00:00:00 2001
From: Adam Nelson <nelsonag@umich.edu>
Date: Tue, 8 Nov 2016 18:52:39 -0500
Subject: [PATCH] Whoops, missed one

---
 openmc/data/function.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/openmc/data/function.py b/openmc/data/function.py
index 4a1f9d7a38..b1cdb09de0 100644
--- a/openmc/data/function.py
+++ b/openmc/data/function.py
@@ -427,9 +427,9 @@ class Combination(EqualityMixin):
         self.operations = operations
 
     def __call__(self, x):
-        ans = np.zeros_like(x)
-        for op, func in zip(self.operations, self.functions):
-            ans = op(ans, func(x))
+        ans = self.functions[0](x)
+        for i, operation in enumerate(self.operations):
+            ans = operation(ans, self.functions[i + 1](x))
         return ans
 
     @property
@@ -448,7 +448,7 @@ class Combination(EqualityMixin):
     @operations.setter
     def operations(self, operations):
         cv.check_type('operations', operations, Iterable, np.ufunc)
-        length = len(self.functions)
+        length = len(self.functions) - 1
         cv.check_length('operations', operations, length, length_max=length)
         self._operations = operations