From cd14b919d3f15e2bb686fdbc0715ec269aa9d3a1 Mon Sep 17 00:00:00 2001
From: Andreas Kloeckner <kloeckner@hpcgeek.ccv.brown.edu>
Date: Thu, 7 May 2009 01:05:09 -0400
Subject: [PATCH] Add equality predicate to single_valued().

---
 pytools/__init__.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pytools/__init__.py b/pytools/__init__.py
index 7054e3a..819162f 100644
--- a/pytools/__init__.py
+++ b/pytools/__init__.py
@@ -297,7 +297,7 @@ def one(iterable):
 
 
 
-def single_valued(iterable):
+def single_valued(iterable, equality_pred=operator.eq):
     it = iter(iterable)
     try:
         first_item = it.next()
@@ -306,7 +306,7 @@ def single_valued(iterable):
 
     def others_same():
         for other_item in it:
-            if other_item != first_item:
+            if not equality_pred(other_item, first_item):
                 raise ValueError, "non-single-valued iterable passed to 'single_valued()'"
         return True
     assert others_same()
-- 
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