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"Purescript by Example"5 장의 예제를 기반으로하는 함수로 재생하고 다형성 행 유형을 선언하는 방법에 대해 다소 혼란스러워합니다.Purescript 행 다형성. 올바른 구문은 무엇입니까?
다음은
type Student = {
first :: String,
last :: String,
class :: String
}
type GymMember = {
first :: String,
last :: String,
benchPressPB :: Int
}
daveG :: GymMember
daveG = {
first: "Dave",
last: "Bro",
benchPressPB: 300
}
philS :: Student
philS = {
first : "Dave",
last : "Swat",
class : "1A"
}
schoolRollName :: forall t15.
{ last :: String
, first :: String
| t15
} -> String
schoolRollName rec = rec.last <> ", " <> rec.first
firstAndSurname :: forall t82.
{ first :: String
, last :: String
| t82
}
-> String
firstAndSurname rec = rec.first <> " " <> rec.last
daveFandS :: String
daveFandS = firstAndSurname daveG
daveSR :: String
daveSR = schoolRollName daveG
philFandS :: String
philFandS = firstAndSurname philS
philSR :: String
philSR = schoolRollName philS
잘 컴파일하지만 어떻게 schoolRollName과 firstAndSurname의 유형 서명의 중복을 제거 할 수 있습니까.
type NamedThing = forall t15.
{ last :: String
, first :: String
| t15
}
schoolRollName :: NamedThing -> String
schoolRollName rec = rec.last <> ", " <> rec.first
firstAndSurname :: NamedThing -> String
firstAndSurname rec = rec.first <> " " <> rec.last
-- !! Could not match type
daveFandS :: String
daveFandS = firstAndSurname daveG