Added simple test cases for string selector with logical ops

Also fixed found bug (missing return statement)

NB: the grammar is not finalized yet

cadquery/selectors.py

@@ -641,7 +641,7 @@ def _makeExpressionGrammar(atom):
     
     def delta_callback(res):
         items = res.asList()[0][::2]
-        reduce(SubtractSelector,items)
+        return reduce(SubtractSelector,items)
         
     def not_callback(res):
         right = res.asList()[0][1]

tests/TestCQSelectors.py

@@ -355,6 +355,16 @@ class TestCQSelectors(BaseTest):
         el = c.edges(S("|X") + S("|Y")).vals()
         self.assertEqual(8, len(el))
         
+        # test using extended string syntax
+        fl = c.faces(">Z | <Z").vals()
+        self.assertEqual(2, len(fl))
+        el = c.edges("|X | |Y").vals()
+        self.assertEqual(8, len(el))
+        
+        # test using extended string syntax
+        v = c.vertices(">X & >Y").vals()
+        self.assertEqual(2, len(v))
+
     def testSubtractSelector(self):
         c = CQ(makeUnitCube())
 
@@ -367,6 +377,10 @@ class TestCQSelectors(BaseTest):
         fl = c.faces(S("#Z") - S(">X")).vals()
         self.assertEqual(3, len(fl))
         
+        # test using extended string syntax
+        fl = c.faces("#Z ^ >X").vals()
+        self.assertEqual(3, len(fl))
+
     def testInverseSelector(self):
         c = CQ(makeUnitCube())
 
@@ -383,6 +397,12 @@ class TestCQSelectors(BaseTest):
         el = c.faces('>Z').edges(-S('>X')).vals()
         self.assertEqual(3, len(el))
         
+        # test using extended string syntax
+        fl = c.faces('~>Z').vals()
+        self.assertEqual(5, len(fl))
+        el = c.faces('>Z').edges('~>X').vals()
+        self.assertEqual(3, len(el))
+
     def testFaceCount(self):
         c = CQ(makeUnitCube())
         self.assertEqual( 6, c.faces().size() )