Copyright	Josef Svenningsson 2008-2017 (c) The University of Glasgow 1994-2000
License	BSD
Maintainer	josef.svenningsson@gmail.com, Andreas Abel
Stability	stable
Portability	non-portable (GHC Extensions)
Safe Haskell	None
Language	Haskell2010

Control.Monad.ST.Trans

Contents

The ST Monad Transformer
Mutable references
Mutable arrays
Unsafe Operations

Description

This library provides a monad transformer version of the ST monad.

Warning! This monad transformer should not be used with monads that can contain multiple answers, like the list monad. The reason is that the state token will be duplicated across the different answers and this causes Bad Things to happen (such as loss of referential transparency). Safe monads include the monads State, Reader, Writer, Maybe and combinations of their corresponding monad transformers.

Synopsis

data STT s m a
runST :: Monad m => (forall s. STT s m a) -> m a
runSTT :: Monad m => (forall s. STT s m a) -> m a
data STRef s a
newSTRef :: Applicative m => a -> STT s m (STRef s a)
readSTRef :: Applicative m => STRef s a -> STT s m a
writeSTRef :: Applicative m => STRef s a -> a -> STT s m ()
data STArray s i e
newSTArray :: (Ix i, Applicative m) => (i, i) -> e -> STT s m (STArray s i e)
readSTArray :: (Ix i, Applicative m) => STArray s i e -> i -> STT s m e
writeSTArray :: (Ix i, Applicative m) => STArray s i e -> i -> e -> STT s m ()
boundsSTArray :: STArray s i e -> (i, i)
numElementsSTArray :: STArray s i e -> Int
freezeSTArray :: Applicative m => STArray s i e -> STT s m (Array i e)
thawSTArray :: Applicative m => Array i e -> STT s m (STArray s i e)
runSTArray :: Monad m => (forall s. STT s m (STArray s i e)) -> m (Array i e)
unsafeReadSTArray :: Applicative m => STArray s i e -> Int -> STT s m e
unsafeWriteSTArray :: Applicative m => STArray s i e -> Int -> e -> STT s m ()
unsafeFreezeSTArray :: Applicative m => STArray s i e -> STT s m (Array i e)
unsafeThawSTArray :: Applicative m => Array i e -> STT s m (STArray s i e)
unsafeIOToSTT :: (Monad m, Functor m) => IO a -> STT s m a
unsafeSTToIO :: STT s IO a -> IO a
unsafeSTTToIO :: STT s IO a -> IO a
unsafeSTRefToIORef :: STRef s a -> IORef a
unsafeIORefToSTRef :: IORef a -> STRef s a

The ST Monad Transformer

data STT s m a Source #

STT is the monad transformer providing polymorphic updateable references

Instances

Instances details

(MonadWriter w m, Functor m) => MonadWriter w (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods writer :: (a, w) -> STT s m a # tell :: w -> STT s m () # listen :: STT s m a -> STT s m (a, w) # pass :: STT s m (a, w -> w) -> STT s m a #
(MonadState s m, Functor m) => MonadState s (STT s1 m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods get :: STT s1 m s # put :: s -> STT s1 m () # state :: (s -> (a, s)) -> STT s1 m a #
(MonadReader r m, Functor m) => MonadReader r (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods ask :: STT s m r # local :: (r -> r) -> STT s m a -> STT s m a # reader :: (r -> a) -> STT s m a #
(MonadError e m, Functor m) => MonadError e (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods throwError :: e -> STT s m a # catchError :: STT s m a -> (e -> STT s m a) -> STT s m a #
MonadTrans (STT s) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods lift :: Monad m => m a -> STT s m a #
(Applicative m, Monad m) => MArray (STUArray s) Word64 (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Word64 -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Word64 -> STT s m Int newArray :: Ix i => (i, i) -> Word64 -> STT s m (STUArray s i Word64) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word64) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word64) unsafeRead :: Ix i => STUArray s i Word64 -> Int -> STT s m Word64 unsafeWrite :: Ix i => STUArray s i Word64 -> Int -> Word64 -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Word32 (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Word32 -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Word32 -> STT s m Int newArray :: Ix i => (i, i) -> Word32 -> STT s m (STUArray s i Word32) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word32) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word32) unsafeRead :: Ix i => STUArray s i Word32 -> Int -> STT s m Word32 unsafeWrite :: Ix i => STUArray s i Word32 -> Int -> Word32 -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Word16 (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Word16 -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Word16 -> STT s m Int newArray :: Ix i => (i, i) -> Word16 -> STT s m (STUArray s i Word16) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word16) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word16) unsafeRead :: Ix i => STUArray s i Word16 -> Int -> STT s m Word16 unsafeWrite :: Ix i => STUArray s i Word16 -> Int -> Word16 -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Word8 (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Word8 -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Word8 -> STT s m Int newArray :: Ix i => (i, i) -> Word8 -> STT s m (STUArray s i Word8) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word8) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word8) unsafeRead :: Ix i => STUArray s i Word8 -> Int -> STT s m Word8 unsafeWrite :: Ix i => STUArray s i Word8 -> Int -> Word8 -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Int64 (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Int64 -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Int64 -> STT s m Int newArray :: Ix i => (i, i) -> Int64 -> STT s m (STUArray s i Int64) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int64) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int64) unsafeRead :: Ix i => STUArray s i Int64 -> Int -> STT s m Int64 unsafeWrite :: Ix i => STUArray s i Int64 -> Int -> Int64 -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Int32 (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Int32 -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Int32 -> STT s m Int newArray :: Ix i => (i, i) -> Int32 -> STT s m (STUArray s i Int32) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int32) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int32) unsafeRead :: Ix i => STUArray s i Int32 -> Int -> STT s m Int32 unsafeWrite :: Ix i => STUArray s i Int32 -> Int -> Int32 -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Int16 (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Int16 -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Int16 -> STT s m Int newArray :: Ix i => (i, i) -> Int16 -> STT s m (STUArray s i Int16) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int16) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int16) unsafeRead :: Ix i => STUArray s i Int16 -> Int -> STT s m Int16 unsafeWrite :: Ix i => STUArray s i Int16 -> Int -> Int16 -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Int8 (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Int8 -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Int8 -> STT s m Int newArray :: Ix i => (i, i) -> Int8 -> STT s m (STUArray s i Int8) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int8) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int8) unsafeRead :: Ix i => STUArray s i Int8 -> Int -> STT s m Int8 unsafeWrite :: Ix i => STUArray s i Int8 -> Int -> Int8 -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Double (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Double -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Double -> STT s m Int newArray :: Ix i => (i, i) -> Double -> STT s m (STUArray s i Double) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Double) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Double) unsafeRead :: Ix i => STUArray s i Double -> Int -> STT s m Double unsafeWrite :: Ix i => STUArray s i Double -> Int -> Double -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Float (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Float -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Float -> STT s m Int newArray :: Ix i => (i, i) -> Float -> STT s m (STUArray s i Float) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Float) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Float) unsafeRead :: Ix i => STUArray s i Float -> Int -> STT s m Float unsafeWrite :: Ix i => STUArray s i Float -> Int -> Float -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Word (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Word -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Word -> STT s m Int newArray :: Ix i => (i, i) -> Word -> STT s m (STUArray s i Word) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Word) unsafeRead :: Ix i => STUArray s i Word -> Int -> STT s m Word unsafeWrite :: Ix i => STUArray s i Word -> Int -> Word -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Int (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Int -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Int -> STT s m Int newArray :: Ix i => (i, i) -> Int -> STT s m (STUArray s i Int) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Int) unsafeRead :: Ix i => STUArray s i Int -> Int -> STT s m Int unsafeWrite :: Ix i => STUArray s i Int -> Int -> Int -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Char (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Char -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Char -> STT s m Int newArray :: Ix i => (i, i) -> Char -> STT s m (STUArray s i Char) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Char) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Char) unsafeRead :: Ix i => STUArray s i Char -> Int -> STT s m Char unsafeWrite :: Ix i => STUArray s i Char -> Int -> Char -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) Bool (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i Bool -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i Bool -> STT s m Int newArray :: Ix i => (i, i) -> Bool -> STT s m (STUArray s i Bool) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Bool) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i Bool) unsafeRead :: Ix i => STUArray s i Bool -> Int -> STT s m Bool unsafeWrite :: Ix i => STUArray s i Bool -> Int -> Bool -> STT s m ()
(Applicative m, Monad m) => MArray (STArray s) e (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STArray s i e -> STT s m (i, i) # getNumElements :: Ix i => STArray s i e -> STT s m Int newArray :: Ix i => (i, i) -> e -> STT s m (STArray s i e) # newArray_ :: Ix i => (i, i) -> STT s m (STArray s i e) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STArray s i e) unsafeRead :: Ix i => STArray s i e -> Int -> STT s m e unsafeWrite :: Ix i => STArray s i e -> Int -> e -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) (StablePtr a) (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i (StablePtr a) -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i (StablePtr a) -> STT s m Int newArray :: Ix i => (i, i) -> StablePtr a -> STT s m (STUArray s i (StablePtr a)) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i (StablePtr a)) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i (StablePtr a)) unsafeRead :: Ix i => STUArray s i (StablePtr a) -> Int -> STT s m (StablePtr a) unsafeWrite :: Ix i => STUArray s i (StablePtr a) -> Int -> StablePtr a -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) (FunPtr a) (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i (FunPtr a) -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i (FunPtr a) -> STT s m Int newArray :: Ix i => (i, i) -> FunPtr a -> STT s m (STUArray s i (FunPtr a)) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i (FunPtr a)) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i (FunPtr a)) unsafeRead :: Ix i => STUArray s i (FunPtr a) -> Int -> STT s m (FunPtr a) unsafeWrite :: Ix i => STUArray s i (FunPtr a) -> Int -> FunPtr a -> STT s m ()
(Applicative m, Monad m) => MArray (STUArray s) (Ptr a) (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STUArray s i (Ptr a) -> STT s m (i, i) # getNumElements :: Ix i => STUArray s i (Ptr a) -> STT s m Int newArray :: Ix i => (i, i) -> Ptr a -> STT s m (STUArray s i (Ptr a)) # newArray_ :: Ix i => (i, i) -> STT s m (STUArray s i (Ptr a)) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STUArray s i (Ptr a)) unsafeRead :: Ix i => STUArray s i (Ptr a) -> Int -> STT s m (Ptr a) unsafeWrite :: Ix i => STUArray s i (Ptr a) -> Int -> Ptr a -> STT s m ()
(Monad m, Functor m) => Monad (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods (>>=) :: STT s m a -> (a -> STT s m b) -> STT s m b # (>>) :: STT s m a -> STT s m b -> STT s m b # return :: a -> STT s m a #
Functor m => Functor (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods fmap :: (a -> b) -> STT s m a -> STT s m b # (<$) :: a -> STT s m b -> STT s m a #
(MonadFix m, Functor m) => MonadFix (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods mfix :: (a -> STT s m a) -> STT s m a #
(MonadFail m, Functor m) => MonadFail (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods fail :: String -> STT s m a #
(Monad m, Functor m) => Applicative (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods pure :: a -> STT s m a # (<>) :: STT s m (a -> b) -> STT s m a -> STT s m b # liftA2 :: (a -> b -> c) -> STT s m a -> STT s m b -> STT s m c # (>) :: STT s m a -> STT s m b -> STT s m b # (<*) :: STT s m a -> STT s m b -> STT s m a #

runST :: Monad m => (forall s. STT s m a) -> m a Source #

Deprecated: Use runSTT instead

Executes a computation in the STT monad transformer

runSTT :: Monad m => (forall s. STT s m a) -> m a Source #

Executes a computation in the STT monad transformer

Mutable references

data STRef s a #

a value of type STRef s a is a mutable variable in state thread s, containing a value of type a

>>> :{
runST (do
    ref <- newSTRef "hello"
    x <- readSTRef ref
    writeSTRef ref (x ++ "world")
    readSTRef ref )
:}
"helloworld"

Instances

Instances details

Eq (STRef s a)

Pointer equality.

Since: base-2.1

Instance details

Defined in GHC.STRef

Methods

(==) :: STRef s a -> STRef s a -> Bool #

(/=) :: STRef s a -> STRef s a -> Bool #

newSTRef :: Applicative m => a -> STT s m (STRef s a) Source #

Create a new reference

readSTRef :: Applicative m => STRef s a -> STT s m a Source #

Reads the value of a reference

writeSTRef :: Applicative m => STRef s a -> a -> STT s m () Source #

Modifies the value of a reference

Mutable arrays

data STArray s i e #

Mutable, boxed, non-strict arrays in the ST monad. The type arguments are as follows:

s: the state variable argument for the ST type
i: the index type of the array (should be an instance of Ix)
e: the element type of the array.

Instances

Instances details

MArray (STArray s) e (ST s)
Instance details Defined in Data.Array.Base Methods getBounds :: Ix i => STArray s i e -> ST s (i, i) # getNumElements :: Ix i => STArray s i e -> ST s Int newArray :: Ix i => (i, i) -> e -> ST s (STArray s i e) # newArray_ :: Ix i => (i, i) -> ST s (STArray s i e) # unsafeNewArray_ :: Ix i => (i, i) -> ST s (STArray s i e) unsafeRead :: Ix i => STArray s i e -> Int -> ST s e unsafeWrite :: Ix i => STArray s i e -> Int -> e -> ST s ()
MArray (STArray s) e (ST s)
Instance details Defined in Data.Array.Base Methods getBounds :: Ix i => STArray s i e -> ST s (i, i) # getNumElements :: Ix i => STArray s i e -> ST s Int newArray :: Ix i => (i, i) -> e -> ST s (STArray s i e) # newArray_ :: Ix i => (i, i) -> ST s (STArray s i e) # unsafeNewArray_ :: Ix i => (i, i) -> ST s (STArray s i e) unsafeRead :: Ix i => STArray s i e -> Int -> ST s e unsafeWrite :: Ix i => STArray s i e -> Int -> e -> ST s ()
(Applicative m, Monad m) => MArray (STArray s) e (STT s m) Source #
Instance details Defined in Control.Monad.ST.Trans.Internal Methods getBounds :: Ix i => STArray s i e -> STT s m (i, i) # getNumElements :: Ix i => STArray s i e -> STT s m Int newArray :: Ix i => (i, i) -> e -> STT s m (STArray s i e) # newArray_ :: Ix i => (i, i) -> STT s m (STArray s i e) # unsafeNewArray_ :: Ix i => (i, i) -> STT s m (STArray s i e) unsafeRead :: Ix i => STArray s i e -> Int -> STT s m e unsafeWrite :: Ix i => STArray s i e -> Int -> e -> STT s m ()
Eq (STArray s i e)	Since: base-2.1
Instance details Defined in GHC.Arr Methods (==) :: STArray s i e -> STArray s i e -> Bool # (/=) :: STArray s i e -> STArray s i e -> Bool #

newSTArray :: (Ix i, Applicative m) => (i, i) -> e -> STT s m (STArray s i e) Source #

Creates a new mutable array

readSTArray :: (Ix i, Applicative m) => STArray s i e -> i -> STT s m e Source #

Retrieves an element from the array

writeSTArray :: (Ix i, Applicative m) => STArray s i e -> i -> e -> STT s m () Source #

Modifies an element in the array

boundsSTArray :: STArray s i e -> (i, i) Source #

Returns the lowest and highest indices of the array

numElementsSTArray :: STArray s i e -> Int Source #

Returns the number of elements in the array

freezeSTArray :: Applicative m => STArray s i e -> STT s m (Array i e) Source #

Copy a mutable array and turn it into an immutable array

thawSTArray :: Applicative m => Array i e -> STT s m (STArray s i e) Source #

Copy an immutable array and turn it into a mutable array

runSTArray :: Monad m => (forall s. STT s m (STArray s i e)) -> m (Array i e) Source #

A safe way to create and work with a mutable array before returning an immutable array for later perusal. This function avoids copying the array before returning it.

Unsafe Operations

unsafeReadSTArray :: Applicative m => STArray s i e -> Int -> STT s m e Source #

unsafeWriteSTArray :: Applicative m => STArray s i e -> Int -> e -> STT s m () Source #

unsafeFreezeSTArray :: Applicative m => STArray s i e -> STT s m (Array i e) Source #

unsafeThawSTArray :: Applicative m => Array i e -> STT s m (STArray s i e) Source #

unsafeIOToSTT :: (Monad m, Functor m) => IO a -> STT s m a Source #

unsafeSTToIO :: STT s IO a -> IO a Source #

Deprecated: Use unsafeSTTToIO instead

unsafeSTTToIO :: STT s IO a -> IO a Source #

unsafeSTRefToIORef :: STRef s a -> IORef a Source #

unsafeIORefToSTRef :: IORef a -> STRef s a Source #