More examples and some minor fixes

tests/test_singular_02.py

@@ -188,6 +188,16 @@ def test_romans(pattern: str, expected: list):
 def test_romans_pcs(pattern: str, expected: list):
     assert get_items(zparse(pattern),len(expected)*2,"pitches") == expected*2
 
+@pytest.mark.parametrize(
+    "pattern,expected",
+    [
+      ("(0 1 2 3 r)+(1)", [1,2,3,4,None]),
+      ("(0 1 2 3 r)-(0 1 4)", [0, -1, -2, -3, None, 1, 0, -1, -2, None, 4, 3, 2, 1, None])
+    ]
+)
+def test_operations(pattern: str, expected: list):
+    assert get_items(zparse(pattern),len(expected)*2,"pitch_class") == expected*2
+
 @pytest.mark.parametrize(
     "pattern,expected",
     [