Newtype型クラス

例を眺めればなんとなくわかる

code:purs(hs)

module Newtype where

import Data.Newtype

import Prelude

import Data.Generic.Rep (class Generic)

import Data.Lens.Iso.Newtype (_Newtype)

import Data.Show.Generic (genericShow)

import Data.String (toUpper)

import Effect.Class.Console (log)

newtype Username = Username String

derive instance Newtype Username _

instance Show Username where

show (Username user) = "Username " <> user

user1 :: Username

user1 = Username "mrsekut"

-- > unwrap user1

-- "mrsekut"

-- > wrap "mrsekut" :: Username

-- Username "mrsekut"

code:purs(hs)

unwrap <<< wrap = id

wrap <<< unwrap = id

k

over

Functorにおけるmapと同じ

code:purs(hs)

upper :: Username -> Username

upper = over Username toUpper

-- > upper $ Username "mrsekut"

-- Username "MRSEKUT"

over2

2引数版

code:purs(hs)

concat :: Username -> Username -> Username

concat = over2 Username (<>)

-- > concat (Username "mrse") (Username "kut")

-- Username mrsekut

overF

liftしたmap

code:purs(hs)

byDomain :: String -> Array Username -> Maybe Username

byDomain = overF Username <<< find <<< contains <<< wrap

-- (Just Username aaa)

overF2

under

under2

underF

underF2

op

ala

与えられたnewtypeのコンテキストで、その関数を適用する

code:purs(hs)

ala'

alaF

code:purs(hs)