Baseline for parser combinators in Haskell

Parser.hs

import qualified Data.Text as T

data Error = EndOfInput | Unexpected Char
 deriving (Eq, Show)

-- Parser from T.Text to some type a.
data Parser a = Parser { runParser :: T.Text -> Either Error (a, T.Text) }

satisfy :: (Char -> Bool) -> Parser Char
satisfy p = Parser $ \input ->
 case T.uncons input of
  Just (c, t) -> if p c then Right (c, t) else Left (Unexpected c)
  Nothing -> Left EndOfInput

char :: Char -> Parser Char
char c = satisfy (== c)