Added some tests for derivative operator precedence.

src/parser.py

@@ -73,7 +73,6 @@ class Parser(BisonParser):
         ('left', ('NEG', )),
         ('right', ('POW', )),
         ('right', ('FUNCTION', )),
-        #('right', ('SIN', 'COS', 'TAN', 'SOLVE', 'INT', 'SQRT')),
         )
 
     interactive = 0

tests/test_parser.py

@@ -70,5 +70,7 @@ class TestParser(unittest.TestCase):
 
         self.assertEqual(tree('d/dx x ^ 2'), der(exp, x))
         self.assertEqual(tree('d / dx x ^ 2'), der(exp, x))
+        self.assertEqual(tree('d/dx x ^ 2 + x'), der(exp, x) + x)
+        self.assertEqual(tree('d/dx (x ^ 2 + x)'), der(exp + x, x))
         self.assertEqual(tree('d/d'), d / d)
         # FIXME: self.assertEqual(tree('d(x ^ 2)/dx'), der(exp, x))