ModuleSTMonadTrans-0.4.8Haskell2010

Control.Monad.ST.Trans

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.

3 types
22 values

PackageSTMonadTrans-0.4.8
Exports25
LanguageHaskell2010
LicenceBSD-3-Clause
SourceTrans.hs

The ST Monad Transformer

3 declarations

newtypenewtype STT s (m :: Type -> Type) a

STT is the monad transformer providing polymorphic updateable references

Instances30MonadError, MonadReader, MonadState, MonadWriter, MonadTrans, MArray, …

(MonadError e m, Functor m) => MonadError e (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(MonadReader r m, Functor m) => MonadReader r (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(MonadState s m, Functor m) => MonadState s (STT s1 m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(MonadWriter w m, Functor m) => MonadWriter w (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
MonadTrans (STT s)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Int16 (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Int32 (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Int64 (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Int8 (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Word16 (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Word32 (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Word64 (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Word8 (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Bool (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Char (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Double (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Float (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Int (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) Word (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STArray s) e (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) (FunPtr a) (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) (Ptr a) (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Applicative m, Monad m) => MArray (STUArray s) (StablePtr a) (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Monad m, Functor m) => Monad (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
Functor m => Functor (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(MonadFix m, Functor m) => MonadFix (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(MonadFail m, Functor m) => MonadFail (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Monad m, Functor m) => Applicative (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(Monad m, Alternative m) => Alternative (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
(MonadIO m, Functor m) => MonadIO (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal

valuerunST :: Monad m => (forall s. STT s m a) -> m a

Deprecated. Use runSTT instead

Executes a computation in the STT monad transformer

valuerunSTT :: Monad m => (forall s. STT s m a) -> m a

Executes a computation in the STT monad transformer

Mutable references

4 declarations

datadata STRef s a

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

Example1 expression

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

Instances1Eq

Eq (STRef s a)Defined in ghc-internal-9.1003.0 · GHC.Internal.STRef
Pointer equality.

valuenewSTRef :: Applicative m => a -> STT s m (STRef s a)

Create a new reference

valuereadSTRef :: Applicative m => STRef s a -> STT s m a

Reads the value of a reference

valuewriteSTRef :: Applicative m => STRef s a -> a -> STT s m ()

Modifies the value of a reference

Mutable arrays

9 declarations

datadata 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.

Instances4MArray, Eq

MArray (STArray s) e (ST s)Defined in array-0.5.8.0 · Data.Array.Base
MArray (STArray s) e (ST s)Defined in array-0.5.8.0 · Data.Array.Base
(Applicative m, Monad m) => MArray (STArray s) e (STT s m)Defined in STMonadTrans-0.4.8 · Control.Monad.ST.Trans.Internal
Eq (STArray s i e)Defined in ghc-internal-9.1003.0 · GHC.Internal.Arr

valuenewSTArray

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

Creates a new mutable array

valuereadSTArray :: (Ix i, Applicative m) => STArray s i e -> i -> STT s m e

Retrieves an element from the array

valuewriteSTArray

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

Modifies an element in the array

valueboundsSTArray :: STArray s i e -> (i, i)

Returns the lowest and highest indices of the array

valuenumElementsSTArray :: STArray s i e -> Int

Returns the number of elements in the array

valuefreezeSTArray :: Applicative m => STArray s i e -> STT s m (Array i e)

Copy a mutable array and turn it into an immutable array

valuethawSTArray :: Applicative m => Array i e -> STT s m (STArray s i e)

Copy an immutable array and turn it into a mutable array

valuerunSTArray

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

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

9 declarations

valueunsafeReadSTArray :: Applicative m => STArray s i e -> Int -> STT s m e

valueunsafeWriteSTArray

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

valueunsafeFreezeSTArray :: Applicative m => STArray s i e -> STT s m (Array i e)

valueunsafeThawSTArray :: Applicative m => Array i e -> STT s m (STArray s i e)

valueunsafeIOToSTT :: (Monad m, Functor m) => IO a -> STT s m a

valueunsafeSTToIO :: STT s IO a -> IO a

Deprecated. Use unsafeSTTToIO instead

valueunsafeSTTToIO :: STT s IO a -> IO a

valueunsafeSTRefToIORef :: STRef s a -> IORef a

valueunsafeIORefToSTRef :: IORef a -> STRef s a