statestack-0.2/0000755000000000000000000000000012236260000011676 5ustar0000000000000000statestack-0.2/Setup.hs0000644000000000000000000000005612236260000013333 0ustar0000000000000000import Distribution.Simple main = defaultMain statestack-0.2/CHANGES.md0000644000000000000000000000013712236260000013271 0ustar00000000000000000.2: XXX -------- * Update to work with latest versions of everything 0.1: Initial release statestack-0.2/LICENSE0000644000000000000000000000276112236260000012711 0ustar0000000000000000Copyright (c)2011, Brent Yorgey All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * Neither the name of Brent Yorgey nor the names of other contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. statestack-0.2/statestack.cabal0000644000000000000000000000163512236260000015035 0ustar0000000000000000Name: statestack Version: 0.2 Synopsis: Simple State-like monad transformer with saveable and restorable state Description: Simple State-like monad transformer where states can be saved to and restored from an internal stack. License: BSD3 License-file: LICENSE Extra-source-files: CHANGES.md Author: Brent Yorgey Maintainer: byorgey@cis.upenn.edu Category: Control Build-type: Simple Cabal-version: >=1.10 Bug-reports: http://github.com/diagrams/statestack/issues Source-repository head type: git location: git://github.com/diagrams/statestack Library Default-language: Haskell2010 Exposed-modules: Control.Monad.StateStack Build-depends: base >= 4.2 && < 4.8, mtl >= 2.1 && < 2.2, transformers >= 0.3 && < 0.4 statestack-0.2/Control/0000755000000000000000000000000012236260000013316 5ustar0000000000000000statestack-0.2/Control/Monad/0000755000000000000000000000000012236260000014354 5ustar0000000000000000statestack-0.2/Control/Monad/StateStack.hs0000644000000000000000000001621712236260000016765 0ustar0000000000000000{-# LANGUAGE GeneralizedNewtypeDeriving , FlexibleInstances , MultiParamTypeClasses #-} ----------------------------------------------------------------------------- -- | -- Module : Control.Monad.StateStack -- Copyright : (c) 2011 Brent Yorgey -- License : BSD-style (see LICENSE) -- Maintainer : byorgey@cis.upenn.edu -- -- A state monad which allows the state to be saved and restored on a -- stack. -- -- [Computation type:] Computations with implicit access to a -- read/write state, with additional operations for pushing the -- current state on a stack and later restoring the state from the top -- of the stack. -- -- [Binding strategy:] Same as for the usual state monad; the state -- and accompanying stack of saved states are threaded through -- computations. -- -- [Useful for:] Remembering state while emitting commands for some -- system which itself has saveable/restorable state, such as OpenGL -- or Cairo. -- -- Simple example: -- -- > ghci> let p = get >>= liftIO . print -- > ghci> evalStateStackT (put 2 >> p >> save >> put 3 >> p >> restore >> p) 0 -- > 2 -- > 3 -- > 2 -- ----------------------------------------------------------------------------- module Control.Monad.StateStack ( -- * The @MonadStateStack@ class MonadStateStack(..) -- * The @StateStackT@ transformer , StateStackT(..), StateStack -- * Running @StateStackT@ and @StateStack@ computations , runStateStackT, evalStateStackT, execStateStackT , runStateStack, evalStateStack, execStateStack , liftState ) where import Data.Monoid import Control.Applicative import Control.Arrow (second) import Control.Monad.Identity import qualified Control.Monad.State as St import Control.Arrow (first, (&&&)) import Control.Monad.Trans import Control.Monad.Trans.Cont import Control.Monad.Trans.Error import Control.Monad.Trans.Identity import Control.Monad.Trans.List import Control.Monad.Trans.Maybe import Control.Monad.Trans.Reader (ReaderT) import Control.Monad.Trans.State.Lazy as Lazy import Control.Monad.Trans.State.Strict as Strict import Control.Monad.Trans.Writer.Lazy as Lazy import Control.Monad.Trans.Writer.Strict as Strict import qualified Control.Monad.Cont.Class as CC -- import qualified Control.Monad.Error.Class as EC import qualified Control.Monad.State.Class as StC -- import qualified Control.Monad.Reader.Class as RC import qualified Control.Monad.IO.Class as IC ------------------------------------------------------------ -- Implementation ------------------------------------------------------------ -- | A monad transformer which adds a save/restorable state to an -- existing monad. newtype StateStackT s m a = StateStackT { unStateStackT :: St.StateT (s,[s]) m a } deriving (Functor, Applicative, Monad, MonadTrans, IC.MonadIO) -- | Class of monads which support a state along with a stack for -- saving and restoring states. class St.MonadState s m => MonadStateStack s m where save :: m () -- ^ Save the current state on the stack restore :: m () -- ^ Restore the top state from the stack instance Monad m => St.MonadState s (StateStackT s m) where get = StateStackT $ St.gets fst put s = StateStackT $ (St.modify . first) (const s) instance Monad m => MonadStateStack s (StateStackT s m) where save = StateStackT $ St.modify (fst &&& uncurry (:)) restore = StateStackT . St.modify $ \(cur,hist) -> case hist of [] -> (cur,hist) (r:hist') -> (r,hist') -- | Run a @StateStackT@ computation from an initial state, resulting -- in a computation of the underlying monad which yields the return -- value and final state. runStateStackT :: Monad m => StateStackT s m a -> s -> m (a, s) runStateStackT m s = (liftM . second) fst . flip St.runStateT (s,[]) . unStateStackT $ m -- | Like 'runStateStackT', but discard the final state. evalStateStackT :: Monad m => StateStackT s m a -> s -> m a evalStateStackT m s = liftM fst $ runStateStackT m s -- | Like 'runStateStackT', but discard the return value and yield -- only the final state. execStateStackT :: Monad m => StateStackT s m a -> s -> m s execStateStackT m s = liftM snd $ runStateStackT m s type StateStack s a = StateStackT s Identity a -- | Run a @StateStack@ computation from an initial state, resulting -- in a pair of the final return value and final state. runStateStack :: StateStack s a -> s -> (a,s) runStateStack m s = runIdentity $ runStateStackT m s -- | Like 'runStateStack', but discard the final state. evalStateStack :: StateStack s a -> s -> a evalStateStack m s = runIdentity $ evalStateStackT m s -- | Like 'runStateStack', but discard the return value and yield -- only the final state. execStateStack :: StateStack s a -> s -> s execStateStack m s = runIdentity $ execStateStackT m s -- | @StateT@ computations can always be lifted to @StateStackT@ -- computations which do not manipulate the state stack. liftState :: Monad m => St.StateT s m a -> StateStackT s m a liftState st = StateStackT . St.StateT $ \(s,ss) -> (liftM . second) (flip (,) ss) (St.runStateT st s) ------------------------------------------------------------ -- Applying monad transformers to MonadStateStack monads ------------------------------------------------------------ instance MonadStateStack s m => MonadStateStack s (ContT r m) where save = lift save restore = lift restore instance (Error e, MonadStateStack s m) => MonadStateStack s (ErrorT e m) where save = lift save restore = lift restore instance MonadStateStack s m => MonadStateStack s (IdentityT m) where save = lift save restore = lift restore instance MonadStateStack s m => MonadStateStack s (ListT m) where save = lift save restore = lift restore instance MonadStateStack s m => MonadStateStack s (MaybeT m) where save = lift save restore = lift restore instance MonadStateStack s m => MonadStateStack s (ReaderT r m) where save = lift save restore = lift restore instance MonadStateStack s m => MonadStateStack s (Lazy.StateT s m) where save = lift save restore = lift restore instance MonadStateStack s m => MonadStateStack s (Strict.StateT s m) where save = lift save restore = lift restore instance (Monoid w, MonadStateStack s m) => MonadStateStack s (Lazy.WriterT w m) where save = lift save restore = lift restore instance (Monoid w, MonadStateStack s m) => MonadStateStack s (Strict.WriterT w m) where save = lift save restore = lift restore ------------------------------------------------------------ -- Applying StateStackT to other monads ------------------------------------------------------------ instance CC.MonadCont m => CC.MonadCont (StateStackT s m) where callCC c = StateStackT $ CC.callCC (unStateStackT . (\k -> c (StateStackT . k))) {- -- These require UndecidableInstances =( instance EC.MonadError e m => EC.MonadError e (StateStackT s m) where throwError = lift . EC.throwError catchError m h = StateStackT $ EC.catchError (unStateStackT m) (unStateStackT . h) instance RC.MonadReader r m => RC.MonadReader r (StateStackT s m) where ask = lift RC.ask local f = StateStackT . RC.local f . unStateStackT -}