Control.Monad.Primitive

Primitive state-transformer monads

Documentation

class Monad m => PrimMonad m where

Class of primitive state-transformer monads

Associated Types

type PrimState m

State token type

Methods

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

Execute a primitive operation

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

Expose the internal structure of the monad

Instances

PrimMonad IO

PrimMonad (ST s)

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

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

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

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

Convert a PrimMonad with a RealWorld state token to IO

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

Convert a PrimMonad to ST

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

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

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

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

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

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

unsafeInlinePrim :: PrimMonad m => m a -> a

unsafeInlineIO :: IO a -> a

unsafeInlineST :: ST s a -> a

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