week11 tweaks

[lambda.git] / assignment8.mdwn

diff --git a/assignment8.mdwn b/assignment8.mdwn
index 495ef2f..59e0090 100644 (file)
--- a/assignment8.mdwn
+++ b/assignment8.mdwn
@@ -2,9 +2,10 @@
 
                type 'a tree = Leaf of 'a | Node of ('a tree * 'a tree)
 
 
                type 'a tree = Leaf of 'a | Node of ('a tree * 'a tree)
 

-               type 'a starred_tree = Root | Starring_Left of 'a starred_pair | Starring_Right of 'a starred_pair
-               and 'a starred_pair = { parent : 'a starred_tree; sibling: 'a tree }
-               and 'a zipper = { tree : 'a starred_tree; filler: 'a tree };;
+               type 'a starred_level = Root | Starring_Left of 'a starred_nonroot | Starring_Right of 'a starred_nonroot
+               and 'a starred_nonroot = { parent : 'a starred_level; sibling: 'a tree };;
+
+               type 'a zipper = { tree : 'a starred_level; filler: 'a tree };;

 
                let rec move_botleft (z : 'a zipper) : 'a zipper =
                        (* returns z if the targetted node in z has no children *)
 
                let rec move_botleft (z : 'a zipper) : 'a zipper =
                        (* returns z if the targetted node in z has no children *)