HeadedMegaparsec

>>> import Prelude>>> import Control.Applicative>>> import Data.Void>>> import qualified Text.Megaparsec as M>>> import qualified Text.Megaparsec.Char as M>>> import qualified Text.Megaparsec.Char.Lexer as ML>>> :{  let    select :: HeadedParsec Void String (Maybe [Either Char Int], Maybe Int)    select = do      string' "select"      endHead      _targets <- optional (space1 *> targets)      _limit <- optional (space1 *> limit)      return (_targets, _limit)      where        -- Lifted versions of basic parsers:        char = parse . M.char        space = parse M.space        space1 = parse M.space1        decimal = parse ML.decimal        string' = parse . M.string'        -- Syntax parsers:        targets = M.sepBy1 target commaSeparator        target = Left <$> char '*' <|> Right <$> decimal        commaSeparator = space *> char ',' *> endHead *> space        limit = string' "limit" *> endHead *> space1 *> decimal    test :: String -> IO ()    test = M.parseTest (toParsec select <* M.eof):}

>>> test "select 1, "1:11:  |1 | select 1,  |           ^unexpected end of inputexpecting '*', integer, or white space

>>> test "select limit "...unexpected end of inputexpecting integer or white space

>>> test "select 1, 2 limit 2"(Just [Right 1,Right 2],Just 2)