Complete 1.01.e.1.c: demo unbalanced behaviour

[tiger.ml.git] / exercises / ch01 / tree.ml

diff --git a/exercises/ch01/tree.ml b/exercises/ch01/tree.ml
index 7cc7d8c..94c2924 100644 (file)
--- a/exercises/ch01/tree.ml
+++ b/exercises/ch01/tree.ml
@@ -1,42 +1,83 @@
 module Array = ArrayLabels
+module List = ListLabels
 
 module type TREE = sig
-  type 'a t
+  type ('k, 'v) t
 
-  val empty : 'a t
+  val empty : ('k, 'v) t
 
-  val add : 'a t -> 'a -> 'a t
+  val set : ('k, 'v) t -> k:'k -> v:'v -> ('k, 'v) t
 
-  val member : 'a t -> 'a -> bool
+  val get : ('k, 'v) t -> k:'k -> 'v option
+
+  val member : ('k, 'v) t -> k:'k -> bool
+
+  val print
+    : ('k, 'v) t
+    -> k_to_string:('k -> string)
+    -> indent_level:string
+    -> unit
 end
 
 module BinaryTree : TREE = struct
-  type 'a t =
-    | Node of 'a * 'a t * 'a t
+  type ('k, 'v) t =
+    | Node of 'k * 'v * ('k, 'v) t * ('k, 'v) t
     | Leaf
 
   let empty = Leaf
 
-  let rec add t x =
+  let rec set t ~k ~v =
+    match t with
+    | Leaf -> Node (k, v, Leaf, Leaf)
+    | Node (k', v', l, r) when k < k' -> Node (k', v', set l ~k ~v, r)
+    | Node (k', v', l, r) when k > k' -> Node (k', v', l, set r ~k ~v)
+    | Node (k, _, l, r) -> Node (k, v, l, r)
+
+  let rec get t ~k =
     match t with
-    | Leaf -> Node (x, Leaf, Leaf)
-    | Node (x', left, right) when x < x' -> Node (x', add left x, right)
-    | Node (x', left, right) when x > x' -> Node (x', left, add right x)
-    | (Node _) as t' -> t'
+    | Leaf -> None
+    | Node (k', _, l, _) when k < k' -> get l ~k
+    | Node (k', _, _, r) when k > k' -> get r ~k
+    | Node (_, v, _, _) -> Some v
 
-  let rec member t x =
+  let rec member t ~k =
     match t with
     | Leaf -> false
-    | Node (x', left, _) when x < x' -> member left x
-    | Node (x', _, right) when x > x' -> member right x
+    | Node (k', _, l, _) when k < k' -> member l ~k
+    | Node (k', _, _, r) when k > k' -> member r ~k
     | Node _ -> true
+
+  let rec fold t ~f ~init:acc =
+    match t with
+    | Leaf -> acc
+    | Node (k, v, l, r) -> fold r ~f ~init:(f (fold l ~f ~init:acc) (k, v))
+
+  let print t ~k_to_string ~indent_level =
+    let (_, nodes) =
+      fold t
+        ~f:(fun (indentation, nodes) (k, _) ->
+            let indentation = indent_level ^ indentation in
+            let node = indentation ^ (k_to_string k) in
+            (indentation, node :: nodes)
+          )
+        ~init:(indent_level, [])
+    in
+    List.iter (List.rev nodes) ~f:print_endline
 end
 
 let () =
-  let tree =
+  let tree_a = BinaryTree.empty in
+  let tree_a = BinaryTree.set tree_a ~k:"k1" ~v:"v1" in
+  let tree_a = BinaryTree.set tree_a ~k:"k2" ~v:"v2" in
+  assert (BinaryTree.member tree_a ~k:"k1");
+  assert (BinaryTree.member tree_a ~k:"k2");
+  assert (Some "v1" = BinaryTree.get tree_a ~k:"k1");
+  assert (Some "v2" = BinaryTree.get tree_a ~k:"k2");
+  let tree_b =
     Array.fold_left
       (Sys.argv)
       ~init:BinaryTree.empty
-      ~f:(fun t str -> BinaryTree.add t str)
+      ~f:(fun t k -> BinaryTree.set t ~k ~v:())
   in
-  Printf.printf "%B\n" (BinaryTree.member tree "a")
+  Printf.printf "%B\n" (BinaryTree.member tree_b ~k:"a");
+  BinaryTree.print tree_b ~k_to_string:(fun x -> x) ~indent_level:"-";