(* 学生ひとり分のデータ（名前、点数、成績）を表す型 *) 
type gakusei_t = { 
  namae : string;       (* 名前 *) 
  tensuu : int;         (* 点数 *) 
  seiseki : string;     (* 成績 *) 
} 
 
(* gakusei_t list 型のデータの例 *) 
let lst1 = [] 
let lst2 = [{namae = "asai"; tensuu = 70; seiseki = "B"}] 
let lst3 = [{namae = "asai"; tensuu = 70; seiseki = "B"}; 
            {namae = "kaneko"; tensuu = 85; seiseki = "A"}] 
let lst4 = [{namae = "yoshida"; tensuu = 80; seiseki = "A"}; 
            {namae = "asai"; tensuu = 70; seiseki = "B"}; 
            {namae = "kaneko"; tensuu = 85; seiseki = "A"}] 
 
(* 目的：学生の成績が A かどうかを調べる *) 
(* is_A : gakusei_t -> bool *) 
let is_A gakusei = match gakusei with 
  {namae = n; tensuu = t; seiseki = s} -> s = "A" 
 
(* 目的：学生リスト lst のうち成績が A の人の数を返す *) 
(* count_A : gakusei_t list -> int *) 
let count_A lst = List.length (List.filter is_A lst) 
 
(* テスト *) 
let test1 = count_A lst1 = 0 
let test2 = count_A lst2 = 0 
let test3 = count_A lst3 = 1 
let test4 = count_A lst4 = 2