Control.Monad.Primitive

Primitive state-transformer monads

Documentation

class Monad m => PrimMonad m where

Class of monads which can perform primitive state-transformer actions

Associated Types

type PrimState m

State token type

Methods

primitive :: (State# (PrimState m) -> (#State# (PrimState m), a#)) -> m a

Execute a primitive operation

Instances

PrimMonad IO

PrimMonad (ST s)

PrimMonad m => PrimMonad (MaybeT m)

PrimMonad m => PrimMonad (ListT m)

PrimMonad m => PrimMonad (IdentityT m)

(Monoid w, PrimMonad m) => PrimMonad (WriterT w m)

(Monoid w, PrimMonad m) => PrimMonad (WriterT w m)

PrimMonad m => PrimMonad (StateT s m)

PrimMonad m => PrimMonad (StateT s m)

PrimMonad m => PrimMonad (ReaderT r m)

(Error e, PrimMonad m) => PrimMonad (ErrorT e m)

(Monoid w, PrimMonad m) => PrimMonad (RWST r w s m)

(Monoid w, PrimMonad m) => PrimMonad (RWST r w s m)

data RealWorld :: *

RealWorld is deeply magical. It is primitive, but it is not unlifted (hence ptrArg). We never manipulate values of type RealWorld; it's only used in the type system, to parameterise State#.

Instances

Typeable * RealWorld

primitive_ :: PrimMonad m => (State# (PrimState m) -> State# (PrimState m)) -> m ()

Execute a primitive operation with no result

class PrimMonad m => PrimBase m where

Class of primitive monads for state-transformer actions.

Unlike PrimMonad, this typeclass requires that the Monad be fully expressed as a state transformer, therefore disallowing other monad transformers on top of the base IO or ST.

Methods

internal :: m a -> State# (PrimState m) -> (#State# (PrimState m), a#)

Expose the internal structure of the monad

Instances

PrimBase IO

PrimBase (ST s)

liftPrim :: (PrimBase m1, PrimMonad m2, PrimState m1 ~ PrimState m2) => m1 a -> m2 a

Lifts a PrimBase into another PrimMonad with the same underlying state token type.

primToPrim :: (PrimBase m1, PrimMonad m2, PrimState m1 ~ PrimState m2) => m1 a -> m2 a

Convert a PrimBase to another monad with the same state token.

primToIO :: (PrimBase m, PrimState m ~ RealWorld) => m a -> IO a

Convert a PrimBase with a RealWorld state token to IO

primToST :: PrimBase m => m a -> ST (PrimState m) a

Convert a PrimBase to ST

unsafePrimToPrim :: (PrimBase m1, PrimMonad m2) => m1 a -> m2 a

Convert a PrimBase to another monad with a possibly different state token. This operation is highly unsafe!

unsafePrimToIO :: PrimBase m => m a -> IO a

Convert any PrimBase to IO. This operation is highly unsafe!

unsafePrimToST :: PrimBase m => m a -> ST s a

Convert any PrimBase to ST with an arbitrary state token. This operation is highly unsafe!

unsafeInlinePrim :: PrimBase m => m a -> a

unsafeInlineIO :: IO a -> a

unsafeInlineST :: ST s a -> a

touch :: PrimMonad m => a -> m ()