(* あらかじめ sect17_2/tree.ml を読み込んでおく必要あり *) 
#use "sect17_2/tree.ml" (* tree_t の定義 *) 
 
(* 木の例 *) 
let tree1 = Empty 
let tree2 = Leaf (3) 
let tree3 = Node (tree1, 4, tree2) 
let tree4 = Node (tree2, 5, tree3) 
 
(* 目的：tree の各要素に f を適用した木を返す *) 
(* tree_map : (int -> int) -> tree_t -> tree_t *) 
let rec tree_map f tree = match tree with 
    Empty -> Empty 
  | Leaf (n) -> Leaf (f n) 
  | Node (t1, n, t2) -> Node (tree_map f t1, f n, tree_map f t2) 
 
(* テスト *) 
let test1 = tree_map (fun x -> x) tree1 = Empty 
let test2 = tree_map (fun x -> x + 1) tree2 = Leaf (4) 
let test3 = tree_map (fun x -> x * 3) tree3 = Node (Empty, 12, Leaf (9)) 
let test4 = tree_map (fun x -> x * 2) tree4 
	    = Node (Leaf (6), 10, Node (Empty, 8, Leaf (6)))