reverting r31508. Add a comment explaining why sets cant be used for a

cleaner algorithm


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@31509 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/TradeCondition.py

@@ -148,11 +148,14 @@ class TradeCondition(Path, Transformation, XMLMatrix):
           # it is possible, that specialised object cannot be specialised
           # anymore
           continue
-        difference = set(child_specialised_value_list).difference(\
+        # Use a set for faster lookups. We do not use sets everywhere
+        # because search order does matter
+        intersection = set(child_specialised_value_list).intersection(\
             set(visited_trade_condition_list))
+        for model in child_specialised_value_list:
           # don't add model that have already been visited. This permit to
           # visit all the tree and to prevent having circular dependency
-        for model in difference:
+          if model not in intersection:
             specialise_value_list.append(model)
             # only add those who matches the portal type given
             if model in child_visited_trade_condition_list: