diff options
Diffstat (limited to 'Control/Monad/Ref.hs')
-rw-r--r-- | Control/Monad/Ref.hs | 171 |
1 files changed, 163 insertions, 8 deletions
diff --git a/Control/Monad/Ref.hs b/Control/Monad/Ref.hs index 01b2f04..c35b757 100644 --- a/Control/Monad/Ref.hs +++ b/Control/Monad/Ref.hs @@ -33,25 +33,50 @@ -- Maintainer : mainland@eecs.harvard.edu -- -- Stability : experimental --- Portability : non-portable (uses Control.Monad.ST) --- --- Mutable references in the (strict) ST monad. +-- Portability : non-portable -- -------------------------------------------------------------------------------- {-# LANGUAGE TypeFamilies #-} module Control.Monad.Ref ( - MonadRef(..) + MonadRef(..), + MonadAtomicRef(..) ) where -import Control.Monad.ST -import Data.IORef -import Data.STRef +import Control.Concurrent.STM (STM) +import Control.Concurrent.STM.TVar (TVar, + newTVar, + readTVar, + writeTVar) +import Control.Monad.ST (ST) +import Control.Monad.Trans.Cont (ContT) +import Control.Monad.Trans.Error (ErrorT, Error) +import Control.Monad.Trans.Identity (IdentityT) +import Control.Monad.Trans.List (ListT) +import Control.Monad.Trans.Maybe (MaybeT) +import Control.Monad.Trans.Reader (ReaderT) +import Control.Monad.Trans.State.Lazy as Lazy (StateT) +import Control.Monad.Trans.State.Strict as Strict (StateT) +import Control.Monad.Trans.Writer.Lazy as Lazy (WriterT) +import Control.Monad.Trans.Writer.Strict as Strict (WriterT) +import Control.Monad.Trans.Class (lift) +import Data.IORef (IORef, + atomicModifyIORef, + modifyIORef, + newIORef, + readIORef, + writeIORef) +import Data.Monoid (Monoid) +import Data.STRef (STRef, + modifySTRef, + newSTRef, + readSTRef, + writeSTRef) -- |The 'MonadRef' type class abstracts over the details of manipulating -- references, allowing one to write code that uses references and can operate --- in either the ST monad or the IO monad. +-- in any monad that supports reference operations. class (Monad m) => MonadRef m where type Ref m :: * -> * @@ -66,6 +91,10 @@ class (Monad m) => MonadRef m where modifyRef :: Ref m a -> (a -> a) -> m () modifyRef r f = readRef r >>= writeRef r . f +class (MonadRef m) => MonadAtomicRef m where + -- |Atomically mutate the contents of a reference + atomicModifyRef :: Ref m a -> (a -> (a, b)) -> m b + instance MonadRef (ST s) where type Ref (ST s) = STRef s @@ -81,3 +110,129 @@ instance MonadRef IO where readRef = readIORef writeRef = writeIORef modifyRef = modifyIORef + +instance MonadRef STM where + type Ref STM = TVar + + newRef = newTVar + readRef = readTVar + writeRef = writeTVar + +instance MonadRef m => MonadRef (ContT r m) where + type Ref (ContT r m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance (Error e, MonadRef m) => MonadRef (ErrorT e m) where + type Ref (ErrorT e m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance MonadRef m => MonadRef (IdentityT m) where + type Ref (IdentityT m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance MonadRef m => MonadRef (ListT m) where + type Ref (ListT m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance MonadRef m => MonadRef (MaybeT m) where + type Ref (MaybeT m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance MonadRef m => MonadRef (ReaderT r m) where + type Ref (ReaderT r m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance MonadRef m => MonadRef (Lazy.StateT s m) where + type Ref (Lazy.StateT s m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance MonadRef m => MonadRef (Strict.StateT s m) where + type Ref (Strict.StateT s m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance (Monoid w, MonadRef m) => MonadRef (Lazy.WriterT w m) where + type Ref (Lazy.WriterT w m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance (Monoid w, MonadRef m) => MonadRef (Strict.WriterT w m) where + type Ref (Strict.WriterT w m) = Ref m + + newRef r = lift $ newRef r + readRef r = lift $ readRef r + writeRef r x = lift $ writeRef r x + modifyRef r f = lift $ modifyRef r f + +instance MonadAtomicRef IO where + atomicModifyRef = atomicModifyIORef + +instance MonadAtomicRef STM where + atomicModifyRef r f = do x <- readRef r + let (x', y) = f x + writeRef r x' + return y + +instance MonadAtomicRef m => MonadAtomicRef (ContT r m) where + atomicModifyRef r f = lift $ atomicModifyRef r f + +instance (Error e, MonadAtomicRef m) => MonadAtomicRef (ErrorT e m) where + atomicModifyRef r f = lift $ atomicModifyRef r f + +instance MonadAtomicRef m => MonadAtomicRef (IdentityT m) where + atomicModifyRef r f = lift $ atomicModifyRef r f + +instance MonadAtomicRef m => MonadAtomicRef (ListT m) where + atomicModifyRef r f = lift $ atomicModifyRef r f + +instance MonadAtomicRef m => MonadAtomicRef (MaybeT m) where + atomicModifyRef r f = lift $ atomicModifyRef r f + +instance MonadAtomicRef m => MonadAtomicRef (ReaderT r m) where + atomicModifyRef r f = lift $ atomicModifyRef r f + +instance MonadAtomicRef m => MonadAtomicRef (Lazy.StateT s m) where + atomicModifyRef r f = lift $ atomicModifyRef r f + +instance MonadAtomicRef m => MonadAtomicRef (Strict.StateT s m) where + atomicModifyRef r f = lift $ atomicModifyRef r f + +instance (Monoid w, MonadAtomicRef m) => MonadAtomicRef (Lazy.WriterT w m) where + atomicModifyRef r f = lift $ atomicModifyRef r f + +instance (Monoid w, MonadAtomicRef m) => MonadAtomicRef (Strict.WriterT w m) where + atomicModifyRef r f = lift $ atomicModifyRef r f |