{-# LANGUAGE FlexibleInstances, Safe #-} {- This module is part of Chatty. Copyleft (c) 2014 Marvin Cohrs All wrongs reversed. Sharing is an act of love, not crime. Please share Antisplice with everyone you like. Chatty is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. Chatty is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details. You should have received a copy of the GNU Affero General Public License along with Chatty. If not, see <http://www.gnu.org/licenses/>. -} -- | Provides a typeclass for buffered scanners as well as a buffering monad transformer. module Text.Chatty.Scanner.Buffered where import Control.Applicative import Control.Monad import Control.Monad.IO.Class import Control.Monad.State import Control.Monad.Trans.Class import Text.Chatty.Scanner -- | Typeclass for all buffered 'ChScanner's. class ChScanner m => ChBufferedScanner m where -- | Scan the next character without removing it. mpeek1 :: m Char -- | Prepend the given character to the scannable input. mprepend :: String -> m () -- | Typeclass for all 'BufferedScanner's with support for pushing and popping. class ChBufferedScanner m => ChStackBufferedScanner m where -- | Push the current input state to the stack. mpush :: m () -- | Pop the previous input state from the stack. mpop :: m () instance Monad m => ChBufferedScanner (StateT String m) where mpeek1 = gets head mprepend s = modify (s++) instance Monad m => ChBufferedScanner (HereStringT m) where mpeek1 = HereString $ \ss -> return (head ss, ss) mprepend s = HereString $ \ss -> return ((), s++ss) -- | A buffering 'MonadScanner' transformer that lets you use 'mpeek1' and 'mprepend' everywhere. newtype ScannerBufferT m a = ScannerBuffer { runScannerBufferT :: [String] -> m (a,[String]) } instance Monad m => Monad (ScannerBufferT m) where return a = ScannerBuffer $ \s -> return (a,s) (ScannerBuffer c) >>= f = ScannerBuffer $ \s -> do (a,s') <- c s; runScannerBufferT (f a) s' instance MonadTrans ScannerBufferT where lift m = ScannerBuffer $ \s -> do a <- m; return (a,s) instance Monad m => Functor (ScannerBufferT m) where fmap = liftM instance Monad m => Applicative (ScannerBufferT m) where (<*>) = ap pure = return instance ChScanner m => ChScanner (ScannerBufferT m) where mscan1 = ScannerBuffer $ \(ss:sx) -> (if null ss then do s <- mscan1; return (s,[]:map (s:) sx) else return (head ss,tail ss:map (head ss:) sx)) mscanL = ScannerBuffer $ \(ss:sx) -> do l <- mscanL; return (ss++l, []:map (++l) sx) mscannable = ScannerBuffer $ \(ss:sx) -> (if null ss then do b <- mscannable; return (b,[]:sx) else return (True,ss:sx)) mscanh = return Nothing mready = ScannerBuffer $ \(ss:sx) -> (if null ss then do b <- mready; return (b,[]:sx) else return (True,ss:sx)) instance MonadIO m => MonadIO (ScannerBufferT m) where liftIO = lift . liftIO instance ChScanner m => ChBufferedScanner (ScannerBufferT m) where mpeek1 = ScannerBuffer $ \(ss:sx) -> (if null ss then do s <- mscan1; return (s,[s]:sx) else return (head ss,ss:sx)) mprepend s = ScannerBuffer $ \(ss:sx) -> return ((),(s++ss):sx) instance ChScanner m => ChStackBufferedScanner (ScannerBufferT m) where mpush = ScannerBuffer $ \(ss:sx) -> return ((),ss:[]:sx) mpop = ScannerBuffer $ \(_:sx) -> return ((),sx)