血液型がAの人物の数を返す関数 count_ketsueki_A

c9_7.ml

(* 日付を表現するレコード *)
type date_t = {
  month: int;
  day:   int;
}

(* 人物を表現するレコード *)
type person_t = {
  height:   float;
  weight:   float;
  birthday: date_t;
  blood:    string;
}

(* 目的:血液型がAの人物の数を返す関数 *)
(* count_ketsueki_A : person_t list -> int *)
let rec count_ketsueki_A persons =
  match persons with
    []                      -> 0
  | { blood = "A" } :: rest -> 1 + count_ketsueki_A rest 
  | _               :: rest -> 0 + count_ketsueki_A rest;;

let people = [{height=1.73;
               weight=73.2;
               birthday = { month=10; day=8; };
               blood    = "A";};
              {height   = 1.60;
               weight   = 59.2;
               birthday = { month=12; day=15; };
               blood    = "A";};
              {height   = 1.64;
               weight   = 50.4;
               birthday = { month=8; day=17; };
               blood    = "O";};
              {height   = 1.73;
               weight   = 73.2;
               birthday = { month=1; day=8; };
               blood    = "A";};
              {height   = 1.60;
               weight   = 59.2;
               birthday = { month=2; day=15; };
               blood    = "A";};
              {height   = 1.64;
               weight   = 50.4;
               birthday = { month=3; day=17; };
               blood    = "O";};
              {height   = 1.73;
               weight   = 73.2;
               birthday = { month=4; day=8; };
               blood    = "A";};
              {height   = 1.60;
               weight   = 59.2;
               birthday = { month=5; day=15; };
               blood    = "A";};
              {height   = 1.64;
               weight   = 50.4;
               birthday = { month=6; day=17; };
               blood    = "O";};
              {height   = 1.73;
               weight   = 73.2;
               birthday = { month=7; day=8; };
               blood    = "A"; };
              {height   = 1.60;
               weight   = 59.2;
               birthday = { month=8; day=15; };
               blood    = "A"; };
              {height   = 1.64;
               weight   = 50.4;
               birthday = { month=9; day=17; };
               blood    = "O"; };
              {height   = 1.64;
               weight   = 50.4;
               birthday = { month=11; day=17; };
               blood    = "O";}];;

let count_ketsueki_A1 = count_ketsueki_A people = 8;;