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-1.	Complete the definitions of `move_botleft` and `move_right_or_up` from the same-fringe solution in the [[week11]] notes. Test your attempts against some example trees to see if the resulting `make_fringe_enumerator` and `same_fringe` functions work as expected.
-
-		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 };;
-
-		let rec move_botleft (z : 'a zipper) : 'a zipper =
-			(* returns z if the targetted node in z has no children *)
-			(* else returns move_botleft (zipper which results from moving down and left in z) *)
-			YOU SUPPLY THE DEFINITION
-
-
-		let rec move_right_or_up (z : 'a zipper) : 'a zipper option =
-			(* if it's possible to move right in z, returns Some (the result of doing so) *)
-			(* else if it's not possible to move any further up in z, returns None *)
-			(* else returns move_right_or_up (result of moving up in z) *)
-			YOU SUPPLY THE DEFINITION
-
-
-		let new_zipper (t : 'a tree) : 'a zipper =
-			{tree = Root; filler = t}
-			;;
-
-		let make_fringe_enumerator (t: 'a tree) =
-			(* create a zipper targetting the root of t *)
-			let zstart = new_zipper t
-			in let zbotleft = move_botleft zstart
-			(* create a refcell initially pointing to zbotleft *)
-			in let zcell = ref (Some zbotleft)
-			(* construct the next_leaf function *)
-			in let next_leaf () : 'a option =
-				match !zcell with
-				| None -> (* we've finished enumerating the fringe *)
-					None
-				| Some z -> (
-					(* extract label of currently-targetted leaf *)
-					let Leaf current = z.filler
-					(* update zcell to point to next leaf, if there is one *)
-					in let () = zcell := match move_right_or_up z with
-						| None -> None
-						| Some z' -> Some (move_botleft z')
-					(* return saved label *)
-					in Some current
-				)
-			(* return the next_leaf function *)
-			in next_leaf
-			;;
-
-		let same_fringe (t1 : 'a tree) (t2 : 'a tree) : bool =
-			let next1 = make_fringe_enumerator t1
-			in let next2 = make_fringe_enumerator t2
-			in let rec loop () : bool =
-				match next1 (), next2 () with
-				| Some a, Some b when a = b -> loop ()
-				| None, None -> true
-				| _ -> false
-			in loop ()
-			;;
-