diff --git a/lib/binary_search/pure.rb b/lib/binary_search/pure.rb
index eb3766b..6898de7 100644
--- a/lib/binary_search/pure.rb
+++ b/lib/binary_search/pure.rb
@@ -7,6 +7,10 @@ def binary_search(&block)
     index = binary_chop(&block)
     index ? self[index] : nil
   end
+  
+  def binary_search_index(&block)
+    binary_chop(&block)
+  end
 
   private
 
@@ -15,7 +19,7 @@ def binary_chop(&block)
     lower = 0
 
     while(upper >= lower) do
-      idx = lower + (upper - lower) / 2
+      idx = lower + ((upper - lower) / 2)
       comp = yield self[idx]
 
       if comp == 0