Add __mod__ operator to UntypedAtomic class

elementpath/datatypes.py

@@ -1001,6 +1001,9 @@ class UntypedAtomic(object):
     def __abs__(self):
         return abs(self.value)
 
+    def __mod__(self, other):
+        return operator.mod(*self._get_operands(other))
+
     if PY3:
         def __str__(self):
             return str(self.value)

elementpath/xpath1_parser.py

@@ -449,11 +449,11 @@ def evaluate(self, context=None):
     if varname in self.parser.variables:
         return self.parser.variables[varname]
     elif context is None:
-        return None
+        return
     elif varname in context.variables:
         return context.variables[varname]
     elif isinstance(context, XPathSchemaContext):
-        return None
+        return
     else:
         raise ElementPathNameError('unknown variable', token=self)
 

tests/test_datatypes.py

@@ -97,6 +97,13 @@ class UntypedAtomicTest(unittest.TestCase):
         self.assertEqual(9.0 / UntypedAtomic('3'), 3.0)
         self.assertEqual(UntypedAtomic('15') * UntypedAtomic('4'), 60)
 
+    def test_abs(self):
+        self.assertEqual(abs(UntypedAtomic(-10)), 10)
+
+    def test_mod(self):
+        self.assertEqual(UntypedAtomic(1) % 2, 1)
+        self.assertEqual(UntypedAtomic('1') % 2, 1.0)
+
 
 class DateTimeTypesTest(unittest.TestCase):