{-# LANGUAGE NoImplicitPrelude #-} module Data.Digit.DF( DF(..) , parseF ) where import Papa import Text.Parser.Char(CharParsing, char) import Text.Parser.Combinators((<?>)) -- $setup -- >>> import Text.Parsec(parse, ParseError, eof) -- >>> import Data.Void(Void) -- >>> import Data.Digit.DigitF class DF d where dF :: Prism' d () xF :: d xF = dF # () instance DF () where dF = id -- | -- -- >>> parse (parseF <* eof) "test" "F" :: Either ParseError (DigitF ()) -- Right (DigitF ()) -- -- >>> parse parseF "test" "Fxyz" :: Either ParseError (DigitF ()) -- Right (DigitF ()) -- -- >>> isn't _Right (parse parseF "test" "xyz" :: Either ParseError (DigitF ())) -- True -- -- prop> \c -> c /= 'F' ==> isn't _Right (parse parseF "test" [c] :: Either ParseError (DigitF ())) parseF :: (DF d, CharParsing p) => p d parseF = xF <$ char 'F' <?> "F" instance DF d => DF (Either d x) where dF = _Left . dF