乙女座の人の名前のみからなるリストを返す関数

c9_8.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 = {
  name:     string;
  height:   float;
  weight:   float;
  birthday: date_t;
  blood:    string;
}

(* 乙女座かどうかを返す *)
(* is_otomeza : date_t -> bool *)
let is_otomeza { month = m; day = d } =
  let x = m * 100 + d in
  0824 <= x && x <= 0923;;

(* 目的:乙女座の人の名前のみからなるリストを返す関数 *)
(* otomeza : person_t list -> string list *)
let rec otomeza persons =
  match persons with
    []                                -> []
  | { name = n; birthday = b } :: ps -> if is_otomeza b then n :: otomeza ps
                                                        else      otomeza ps

let people = [{name     = "ほげ";
               height   = 1.73;
               weight   = 73.2;
               birthday = { month=10; day=8; };
               blood    = "A";};
              {name     = "ふが";
               height   = 1.60;
               weight   = 59.2;
               birthday = { month=12; day=15; };
               blood    = "A";};
              {name     = "みー";
               height   = 1.64;
               weight   = 50.4;
               birthday = { month=8; day=17; };
               blood    = "O";};
              {name     = "ぱー";
               height   = 1.73;
               weight   = 73.2;
               birthday = { month=1; day=8; };
               blood    = "A";};
              {name     = "ぐう";
               height   = 1.60;
               weight   = 59.2;
               birthday = { month=2; day=15; };
               blood    = "A";};
              {name     = "へろ";
               height   = 1.64;
               weight   = 50.4;
               birthday = { month=3; day=17; };
               blood    = "O";};
              {name     = "ぼえ";
               height   = 1.73;
               weight   = 73.2;
               birthday = { month=4; day=8; };
               blood    = "A";};
              {name     = "もょもと";
               height   = 1.60;
               weight   = 59.2;
               birthday = { month=5; day=15; };
               blood    = "A";};
              {name     = "ぱん";
               height   = 1.64;
               weight   = 50.4;
               birthday = { month=6; day=17; };
               blood    = "O";};
              {name     = "ぶー";
               height   = 1.73;
               weight   = 73.2;
               birthday = { month=7; day=8; };
               blood    = "A"; };
              {name     = "てるみん";
               height   = 1.60;
               weight   = 59.2;
               birthday = { month=8; day=15; };
               blood    = "A"; };
              {name     = "ねこ";
               height   = 1.64;
               weight   = 50.4;
               birthday = { month=9; day=17; };
               blood    = "O"; };
              {name     = "がりがりさん";
               height   = 1.64;
               weight   = 50.4;
               birthday = { month=11; day=17; };
               blood    = "O";}];;

let otomeza1 = otomeza people = ["ねこ"];;