Merge pull request #90 from majurg/add-sort-keyword-argument

Add sort keyword argument to DualBase simplify()

Author: pombredanne

boolean/boolean.py

@@ -1135,7 +1135,7 @@ def __contains__(self, expr):
         if isinstance(expr, self.__class__):
             return all(arg in self.args for arg in expr.args)
 
-    def simplify(self):
+    def simplify(self, sort=True):
         """
         Return a new simplified expression in canonical form from this
         expression.
@@ -1254,7 +1254,8 @@ def simplify(self):
             return args[0]
 
         # Commutativity: A & B = B & A, A | B = B | A
-        args.sort()
+        if sort:
+            args.sort()
 
         # Create new (now canonical) expression.
         expr = self.__class__(*args)

boolean/test_boolean.py

@@ -705,6 +705,17 @@ def test_simplify(self):
         # Elimination
         self.assertEqual(a, ((a & ~b) | (a & b)).simplify())
 
+        # Commutativity + Non-Commutativity 
+        sorted_expression = (b & b & a).simplify()
+        unsorted_expression = (b & b & a).simplify(sort=False)
+        self.assertEqual(sorted_expression, unsorted_expression)
+        self.assertNotEqual(sorted_expression.pretty(), unsorted_expression.pretty())
+
+        sorted_expression = (b | b | a).simplify()
+        unsorted_expression = (b | b | a).simplify(sort=False)
+        self.assertEqual(sorted_expression, unsorted_expression)
+        self.assertNotEqual(sorted_expression.pretty(), unsorted_expression.pretty())
+
         expected = algebra1.parse('(a&b)|(b&c)|(a&c)')
         result = algebra1.parse('(~a&b&c) | (a&~b&c) | (a&b&~c) | (a&b&c)', simplify=True)
         self.assertEqual(expected, result)