X-Git-Url: https://git.distorted.org.uk/~mdw/fringe/blobdiff_plain/2bd37ef118cb1e41cb0e9e2332a9eb69ac2f2df4..f6006dc5e1018143a819e480bc8d67786599c57a:/smalltalk-fringe.st

diff --git a/smalltalk-fringe.st b/smalltalk-fringe.st
index 0d319da..653c31a 100644
--- a/smalltalk-fringe.st
+++ b/smalltalk-fringe.st
@@ -5,7 +5,19 @@ Smalltalk implementation of a `same-fringe' solver.
 Use GNU Smalltalk syntax -- it seems more Emacs-friendly.
 "
 
-Object subclass: Node [
+Object subclass: BasicNode [
+    <comment: 'I am provide common behaviour for my subclasses Node and
+LeafNode.  Otherwise, I''m not particularly interesting.'>
+
+    iterator [
+	"Return a new iterator to walk this node."
+
+	<category: 'iteration'>
+	^NodeIterator for: self
+    ]
+]
+
+BasicNode subclass: Node [
     | left right data |
 
     <comment: 'I represent simple binary tree nodes.  My instances consist of
@@ -69,13 +81,6 @@ instances of LeafNode.'>
 	^false
     ]
 
-    iterator [
-	"Answer a new iterator to walk this node."
-
-	<category: 'iteration'>
-	^NodeIterator for: self
-    ]
-
     inorderTell: aBlock tell: aNodeIterator [
 	"This is the hairy part of the iteration protocol.
 
@@ -179,7 +184,7 @@ PositionableStream extend [
     ]
 ]
 
-Object subclass: LeafNode [
+BasicNode subclass: LeafNode [
     <comment: 'I represent the leaves of a tree of Nodes.  I don''t hold any
 kind of interesting state.  My methods provide the base cases for some of the
 recursive protocols used to handle Nodes.'>
@@ -201,13 +206,6 @@ recursive protocols used to handle Nodes.'>
 	^true
     ]
 
-    iterator [
-	"Return a new iterator to walk this node."
-
-	<category: 'iteration'>
-	^NodeIterator for: self
-    ]
-
     inorderTell: aBlock tell: aNodeIterator [
 	"This is the hairy part of the iteration protocol.