Added negation to Leaf representation.

node.py

@@ -22,14 +22,14 @@ class Node(object):
         return len(self.nodes)
 
     def __eq__(self, node):
-        return isinstance(node, Node) \
-               and self.value == node.value and self.nodes == node.nodes
+        return isinstance(node, Node) and self.value == node.value \
+               and self.nodes == node.nodes
 
     def __neg__(self):
-        copy = deepcopy(self)
-        copy.negated += 1
+        copied = deepcopy(self)
+        copied.negated += 1
 
-        return copy
+        return copied
 
     def __str__(self):
         return '<Node value=%s nodes=%s negated=%d>' \
@@ -50,7 +50,7 @@ class Leaf(Node):
         return len(str(self.value))
 
     def __repr__(self):
-        return repr(self.value)
+        return repr('-' * self.negated + str(self.value))
 
     def __str__(self):
-        return '-' * self.negated + str(self.value)
+        return '<Leaf %s>' % repr(self)