From fb8e10f50a4982c7746a3a5323da80286cd822b0 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Mon, 12 Nov 2018 11:13:16 -0600
Subject: [PATCH] Make sure Sum stores a list of functions

---
 openmc/data/function.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/openmc/data/function.py b/openmc/data/function.py
index 3362040dcf..36443e761e 100644
--- a/openmc/data/function.py
+++ b/openmc/data/function.py
@@ -518,7 +518,7 @@ class Sum(EqualityMixin):
     """
 
     def __init__(self, functions):
-        self.functions = functions
+        self.functions = list(functions)
 
     def __call__(self, x):
         return sum(f(x) for f in self.functions)