{-# LANGUAGE NoImplicitPrelude #-}

module Data.Digit.Class.D4(
  D4(..)
, parse4
) where

import Control.Category (id)
import Control.Lens (Prism', (#))

import Data.Functor ((<$))

import Text.Parser.Char(CharParsing, char)
import Text.Parser.Combinators((<?>))

-- $setup
-- >>> import Data.Digit.Class
-- >>> import Text.Parsec(parse, ParseError, eof)
-- >>> import Data.Void(Void)

class D4 d where
  d4 ::
    Prism'
      d
      ()
  x4 ::
    d
  x4 =
    forall d. D4 d => Prism' d ()
d4 forall t b. AReview t b -> b -> t
# ()

instance D4 () where
  d4 :: Prism' () ()
d4 =
    forall {k} (cat :: k -> k -> *) (a :: k). Category cat => cat a a
id
   
-- |
--
-- >>> parse (parse4 <* eof) "test" "4" :: Either ParseError DecDigit
-- Right DecDigit4
--
-- >>> parse parse4 "test" "4xyz" :: Either ParseError DecDigit
-- Right DecDigit4
--
-- >>> isn't _Right (parse parse4 "test" "xyz" :: Either ParseError DecDigit)
-- True
parse4 ::
  (D4 d, CharParsing p) =>
  p d
parse4 :: forall d (p :: * -> *). (D4 d, CharParsing p) => p d
parse4 =
  forall d. D4 d => d
x4 forall (f :: * -> *) a b. Functor f => a -> f b -> f a
<$ forall (m :: * -> *). CharParsing m => Char -> m Char
char Char
'4' forall (m :: * -> *) a. Parsing m => m a -> String -> m a
<?> String
"4"