型の紹介 - カスタム型の作成 - パターンマッチング

開発環境

入門Haskellプログラミング (Will Kurt(著)、株式会社クイープ(監修、翻訳)、翔泳社)の UNIT2(型の紹介)、LESSON 12(カスタム型の作成)、12.4(練習問題)、Q12-1の解答を求めてみる。

コード

sample.hs

import Distribution.PackageDescription (cAnd)
main :: IO ()
main = do
    print $ canDonateToPatient johnDoe jackieSmith
    print $ canDonateToPatient jackieSmith johnDoe

type FirstName = String
type LastName = String
type MiddleName = String
data Name = Name FirstName LastName |
    NameWithMiddleName FirstName MiddleName LastName

data Sex = Male | Female

data RhType = Pos | Neg
data ABOType = A | B | AB | O
data BloodType = BloodType ABOType RhType

data Patient = Patient {
    name :: Name,
    sex :: Sex,
    age :: Int,
    height :: Int,
    weight :: Int,
    bloodType :: BloodType
}
canDonateTo :: BloodType -> BloodType -> Bool
canDonateTo (BloodType O _) _ = True
canDonateTo _ (BloodType AB _) = True
canDonateTo (BloodType A _) (BloodType A _) = True
canDonateTo (BloodType B _) (BloodType B _) = True
canDonateTo _ _ = False

canDonateToPatient :: Patient -> Patient -> Bool
canDonateToPatient p1 p2 =  canDonateTo (bloodType p1) (bloodType p2)

johnDoe :: Patient
johnDoe = Patient {
    name = Name "John" "Doe",
    sex = Male,
    age = 30,
    height = 74,
    weight = 200,
    bloodType = BloodType AB Pos
}
jackieSmith :: Patient
jackieSmith = Patient {
    name = Name "Jackie" "Smith",
    age = 43,
    sex = Female,
    height = 62,
    weight = 115,
    bloodType = BloodType O Neg
}

入出力結果(Terminal, Zsh)

% runghc sample.hs 
False
True
%