examples/Examples.hs · generic-lens

git.iko.soy/generic-lens

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1{-# LANGUAGE DataKinds #-}

2{-# LANGUAGE DeriveGeneric #-}

3{-# LANGUAGE DuplicateRecordFields #-}

4{-# LANGUAGE FlexibleContexts #-}

5{-# LANGUAGE TypeApplications #-}

6{-# LANGUAGE UndecidableInstances #-}

8{-# OPTIONS_GHC -fno-warn-unused-imports #-}

10module Examples where

12import GHC.Generics

13import Data.Generics.Product

14import Control.Lens

16data Animal = Animal

17 { name :: String

18 , age :: Int

19 , eats :: String

20 } deriving (Show, Generic)

22data Human = Human

23 { name :: String

24 , age :: Int

25 , address :: String

26 , eats :: String

27 } deriving (Show, Generic)

29data Living

30 = Animal' { name :: String, eats :: String, age :: Int }

31 | Human' { name :: String, age :: Int, address :: String, eats :: String }

32 deriving (Show, Generic)

34toby :: Human

35toby = Human { name = "Toby", age = 10, address = "London", eats = "Bread" }

37growUp :: Animal -> Animal

38growUp (Animal n a _) = Animal n (a + 10) "raw meat"

40data MyRecord = MyRecord { field1 :: Int, field2 :: String } deriving Generic

42--g :: Subtype s MyRecord => s -> String

43--g s = s ^. super @MyRecord . label @"field2"

45data Test a b = Test { fieldInt :: Int, fieldA :: a, fieldB :: b } deriving (Generic, Show)

47-- changedA :: Test Int String

48-- >>> changedA

49-- Test {fieldInt = 10, fieldA = 10, fieldB = "world"}

50changedA = set (field @"fieldA") (10 :: Int) (Test 10 "hello" "world")

52-- changedB :: Test String Int

53-- >>> changedB

54-- Test {fieldInt = 10, fieldA = "hello", fieldB = 10}

55changedB = set (field @"fieldB") (10 :: Int) (Test 10 "hello" "world")

57--changedInt = set (field @"fieldInt") ("hello") (Test 10 "hello" "world")

58-- type error