Fix union and intersection simplification.

ppp_libmodule/simplification.py

@@ -27,12 +27,12 @@ def simplify_union(tree):
     lists = list(set(itertools.chain(*lists)))
 
     non_lists = list(non_lists)
-    if non_lists: # If there are non-lists (eg. triples)
+    if lists:
         all_ = non_lists
         all_.append(List(lists))
         return Union(all_)
-    else: # If there are only lists
-        return List(lists)
+    else:
+        return List(non_lists)
 
 def simplify_intersection(tree):
     # Trivial cases
@@ -41,18 +41,20 @@ def simplify_intersection(tree):
     elif len(tree.list) == 1:
         return tree.list[0]
 
-    (lists, non_lists) = partition(lambda x:isinstance(x, List), tree.list)
+    (a, b) = partition(lambda x:isinstance(x, (List, Resource)), tree.list)
+    (lists, non_lists) = partition(lambda x:isinstance(x, (List, Resource)),
+                                   tree.list)
     # Make intersection of lists
-    lists = list(map(set, map(operator.attrgetter('list'), lists))) or [set()]
+    lists = [set(x.list) if isinstance(x, List) else {x} for x in lists] or [set()]
     lists = list(lists[0].intersection(*lists[1:]))
 
     non_lists = list(non_lists)
-    if non_lists: # If there are non-lists (eg. triples)
+    if lists:
         all_ = non_lists
-        all_.append(List(lists))
+        all_.append(simplify_list(List(lists)))
         return Intersection(all_)
-    else: # If there are only lists
-        return List(lists)
+    else:
+        return List(non_lists)
 
 def simplify_list(tree):
     if len(tree.list) == 1: