{-# LANGUAGE NoImplicitPrelude #-}

module Data.Digit.Class.D8(
  D8(..)
, parse8
) 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 D8 d where
  d8 ::
    Prism'
      d
      ()
  x8 ::
    d
  x8 =
    forall d. D8 d => Prism' d ()
d8 forall t b. AReview t b -> b -> t
# ()

instance D8 () where
  d8 :: Prism' () ()
d8 =
    forall {k} (cat :: k -> k -> *) (a :: k). Category cat => cat a a
id
    
-- |
--
-- >>> parse (parse8 <* eof) "test" "8" :: Either ParseError DecDigit
-- Right DecDigit8
--
-- >>> parse parse8 "test" "8xyz" :: Either ParseError DecDigit
-- Right DecDigit8
--
-- >>> isn't _Right (parse parse8 "test" "xyz" :: Either ParseError DecDigit)
-- True
parse8 ::
  (D8 d, CharParsing p) =>
  p d
parse8 :: forall d (p :: * -> *). (D8 d, CharParsing p) => p d
parse8 =
  forall d. D8 d => d
x8 forall (f :: * -> *) a b. Functor f => a -> f b -> f a
<$ forall (m :: * -> *). CharParsing m => Char -> m Char
char Char
'8' forall (m :: * -> *) a. Parsing m => m a -> String -> m a
<?> String
"8"