record-lens.hs

{-# LANGUAGE DeriveGeneric, TemplateHaskell #-}

import GHC.Generics
import Control.Lens

data Score = Score
    { _english :: Int
    , _math :: Int
    } deriving (Generic, Show)

data Person = Person
    { _name :: String
    , _score :: Score
    } deriving (Generic, Show)

makeLenses ''Score
makeLenses ''Person

person :: Person
person = Person "lotz" (Score 50 60)

main = do
    print $ person ^.name
    print $ person ^.score.math
    print $ person &score.math.~ 100