Optics.Generic

>>> :{data User a  = User { name :: String         , age  :: a         }  | LazyUser { name :: String             , age  :: a             , lazy :: Bool             }  deriving (Show, Generic):}

>>> let user = User "Tom" 32 :: User Int

>>> user ^. gfield @"name""Tom"

>>> user ^. gfield @"age"32

>>> user ^. gfield @"salary"......Data constructor ‘User’ doesn't have a field named ‘salary’...In the......

>>> user ^. gfield @"lazy"......Data constructor ‘User’ doesn't have a field named ‘lazy’...In the......

>>> user & gfield @"age" .~ ()User {name = "Tom", age = ()}

>>> NoG 'x' ^. gfield @"any"......Type ‘NoG’ doesn't have a Generic instance...In the......

>>> user ^. #name"Tom"

>>> user & #age %~ (+1)User {name = "Tom", age = 33}

>>> :{data Fish = Herring { name :: String }          | Tuna    { name :: String, sleeping :: Bool }  deriving Generic:}

>>> let herring = Herring { name = "Henry" }>>> let tuna    = Tuna { name = "Tony", sleeping = True }

>>> herring ^? gafield @"name"Just "Henry"

>>> herring ^? gafield @"sleeping"Nothing

>>> tuna ^? gafield @"sleeping"Just True

>>> NoG 'x' ^? gafield @"any"......Type ‘NoG’ doesn't have a Generic instance...In the......

>>> tuna ^? gafield @"salary"......Type ‘Fish’ doesn't have a field named ‘salary’...In the......

>>> ('a', 'b', 'c') ^. gposition @2'b'

>>> ('a', 'b') & gposition @1 .~ "hi" & gposition @2 .~ "there"("hi","there")

>>> ('a', 'b', 'c') ^. gposition @4......Data constructor ‘(,,)’ has 3 fields, 4th requested...In the......

>>> () ^. gposition @1......Data constructor ‘()’ has no fields, 1st requested...In the......

>>> NoG 'x' ^. gposition @1......Type ‘NoG’ doesn't have a Generic instance...In the......

>>> ('a', 'b') ^. gposition @0......There is no 0th position...In the......

>>> :{data Animal = Dog { name :: String, age :: Int }            | Cat { name :: String, purrs :: Bool }  deriving (Show, Generic):}

>>> let dog = Dog "Sparky" 2>>> let cat = Cat "Cuddly" True

>>> dog ^? gconstructor @"Dog"Just ("Sparky",2)

>>> dog ^? gconstructor @"Cat"Nothing

>>> cat & gconstructor @"Cat" % _2 %~ notCat {name = "Cuddly", purrs = False}

>>> dog & gconstructor @"Cat" % _1 .~ "Merry"Dog {name = "Sparky", age = 2}

>>> cat ^? gconstructor @"Parrot"......Type ‘Animal’ doesn't have a constructor named ‘Parrot’...In the......

>>> NoG 'x' ^. gconstructor @"NoG"......Type ‘NoG’ doesn't have a Generic instance...In the......

>>> dog ^? #_DogJust ("Sparky",2)

>>> cat & #_Cat % _1 .~ "Merry"Cat {name = "Merry", purrs = True}

>>> toListOf (gplate @Char) ('h', ((), 'e', Just 'l'), "lo")"hello"

>>> toListOf (gplate @String) ("one","two")["one","two"]

>>> let noG = (NoG 'n', (Just 'i', "c"), 'e')

>>> toListOf (gplate @Char) noG"ice"

>>> deriving instance Generic NoG

>>> toListOf (gplate @Char) noG"nice"