10.9.ml

(* 目的:ふたつのリストを受け取って長さが同じかどうかを返す *)
(* equal_length : a' list -> b' list -> bool *)
let rec equal_length lst1 lst2 =
  match lst1 with
    [] -> (match lst2 with [] -> true | _::_ -> false)
  | f1::r1 -> (match lst2 with [] -> false | f2::r2 -> equal_length r1 r2)

(* テスト *)
let test1 = equal_length [] [] = true
let test2 = equal_length [1; 2; 3] ["a";"b";"c"] = true
let test3 = equal_length [] [1;2;3;4] = false