Control.Monad.Allocate

This module defines interfaces for safe resource usage on top of GeneralAllocate, where resources have an arbitrary lifetime and can be released manually or at the end of the computation.

For contexts where nested scope-based allocation and release is sufficient, see Control.Monad.With.

This design is heavily based on MonadResource from resourcet. resourcet is Copyright (c)2011, Michael Snoyman, and licensed under the BSD 3-clause license available at LICENSE.resourcet.

Documentation

class (Monad m, Monad (AllocationContext m)) => MonadAllocate m where

A monad allowing for exception-safe resource usage with arbitrary lifetimes.

The guarantees of MonadAllocate are weaker than MonadResource: in some monads, it's possible for resources not to get cleaned up if the entire monadic computation is going to be aborted (e.g. an async exception sent to a thread executing a monad with no exception catching). Of course, MonadResource itself can't guarantee cleanup in the presence of SIGKILL... In any case, this allows for MonadAllocate to be implemented lawfully in more monads (see NoContinuationResourceT). This allows for writing monad-generic exception-safe code which can be properly instantiated in IO or mocked out in ST without changing the code.

Minimal complete definition

generalAllocate, generalRelease

Associated Types

type AllocationContext m :: Type -> Type

The monad in which resources are allocated and released.

type GeneralReleaseKey m

A handle to release some resource early manually

type AllocationException m

The exception type of the monadic context

type AllocationException m = SomeException

Methods

generalAllocate :: GeneralAllocate (AllocationContext m) (AllocationException m) () () a -> m (GeneralReleaseKey m, a)

Allocate some resource, which will be cleaned up on call to generalRelease or the end of the current resource scope, whichever comes first.

generalRegister :: (GeneralReleaseType (AllocationException m) () -> AllocationContext m ()) -> m (GeneralReleaseKey m)

Register an action which will be guaranteed to run on call to generalRelease or the end of the current resource scope, whichever comes first.

generalRelease :: GeneralReleaseKey m -> AllocationContext m ()

Run a release action from a prior call to generalAllocate/generalRegister.

Instances

MonadResource m => MonadAllocate (AllocateViaResource m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (AllocateViaResource m) :: Type -> Type

type GeneralReleaseKey (AllocateViaResource m)

type AllocationException (AllocateViaResource m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (AllocateViaResource m)) (AllocationException (AllocateViaResource m)) () () a -> AllocateViaResource m (GeneralReleaseKey (AllocateViaResource m), a)

generalRegister :: (GeneralReleaseType (AllocationException (AllocateViaResource m)) () -> AllocationContext (AllocateViaResource m) ()) -> AllocateViaResource m (GeneralReleaseKey (AllocateViaResource m))

generalRelease :: GeneralReleaseKey (AllocateViaResource m) -> AllocationContext (AllocateViaResource m) ()

(PrimMonad m, MonadWith m) => MonadAllocate (NoContinuationResourceT m)

Defined in Control.Monad.NoContinuation.Resource.Internal

Associated Types

type AllocationContext (NoContinuationResourceT m) :: Type -> Type

type GeneralReleaseKey (NoContinuationResourceT m)

type AllocationException (NoContinuationResourceT m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (NoContinuationResourceT m)) (AllocationException (NoContinuationResourceT m)) () () a -> NoContinuationResourceT m (GeneralReleaseKey (NoContinuationResourceT m), a)

generalRegister :: (GeneralReleaseType (AllocationException (NoContinuationResourceT m)) () -> AllocationContext (NoContinuationResourceT m) ()) -> NoContinuationResourceT m (GeneralReleaseKey (NoContinuationResourceT m))

generalRelease :: GeneralReleaseKey (NoContinuationResourceT m) -> AllocationContext (NoContinuationResourceT m) ()

MonadIO m => MonadAllocate (ResourceT m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (ResourceT m) :: Type -> Type

type GeneralReleaseKey (ResourceT m)

type AllocationException (ResourceT m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (ResourceT m)) (AllocationException (ResourceT m)) () () a -> ResourceT m (GeneralReleaseKey (ResourceT m), a)

generalRegister :: (GeneralReleaseType (AllocationException (ResourceT m)) () -> AllocationContext (ResourceT m) ()) -> ResourceT m (GeneralReleaseKey (ResourceT m))

generalRelease :: GeneralReleaseKey (ResourceT m) -> AllocationContext (ResourceT m) ()

MonadAllocate m => MonadAllocate (MaybeT m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (MaybeT m) :: Type -> Type

type GeneralReleaseKey (MaybeT m)

type AllocationException (MaybeT m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (MaybeT m)) (AllocationException (MaybeT m)) () () a -> MaybeT m (GeneralReleaseKey (MaybeT m), a)

generalRegister :: (GeneralReleaseType (AllocationException (MaybeT m)) () -> AllocationContext (MaybeT m) ()) -> MaybeT m (GeneralReleaseKey (MaybeT m))

generalRelease :: GeneralReleaseKey (MaybeT m) -> AllocationContext (MaybeT m) ()

(MonadAllocate m, MonadTrans t, Monad (t m)) => MonadAllocate (AllocateViaLift t m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (AllocateViaLift t m) :: Type -> Type

type GeneralReleaseKey (AllocateViaLift t m)

type AllocationException (AllocateViaLift t m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (AllocateViaLift t m)) (AllocationException (AllocateViaLift t m)) () () a -> AllocateViaLift t m (GeneralReleaseKey (AllocateViaLift t m), a)

generalRegister :: (GeneralReleaseType (AllocationException (AllocateViaLift t m)) () -> AllocationContext (AllocateViaLift t m) ()) -> AllocateViaLift t m (GeneralReleaseKey (AllocateViaLift t m))

generalRelease :: GeneralReleaseKey (AllocateViaLift t m) -> AllocationContext (AllocateViaLift t m) ()

MonadAllocate m => MonadAllocate (ExceptT e m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (ExceptT e m) :: Type -> Type

type GeneralReleaseKey (ExceptT e m)

type AllocationException (ExceptT e m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (ExceptT e m)) (AllocationException (ExceptT e m)) () () a -> ExceptT e m (GeneralReleaseKey (ExceptT e m), a)

generalRegister :: (GeneralReleaseType (AllocationException (ExceptT e m)) () -> AllocationContext (ExceptT e m) ()) -> ExceptT e m (GeneralReleaseKey (ExceptT e m))

generalRelease :: GeneralReleaseKey (ExceptT e m) -> AllocationContext (ExceptT e m) ()

MonadAllocate m => MonadAllocate (ReaderT r m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (ReaderT r m) :: Type -> Type

type GeneralReleaseKey (ReaderT r m)

type AllocationException (ReaderT r m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (ReaderT r m)) (AllocationException (ReaderT r m)) () () a -> ReaderT r m (GeneralReleaseKey (ReaderT r m), a)

generalRegister :: (GeneralReleaseType (AllocationException (ReaderT r m)) () -> AllocationContext (ReaderT r m) ()) -> ReaderT r m (GeneralReleaseKey (ReaderT r m))

generalRelease :: GeneralReleaseKey (ReaderT r m) -> AllocationContext (ReaderT r m) ()

MonadAllocate m => MonadAllocate (StateT s m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (StateT s m) :: Type -> Type

type GeneralReleaseKey (StateT s m)

type AllocationException (StateT s m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (StateT s m)) (AllocationException (StateT s m)) () () a -> StateT s m (GeneralReleaseKey (StateT s m), a)

generalRegister :: (GeneralReleaseType (AllocationException (StateT s m)) () -> AllocationContext (StateT s m) ()) -> StateT s m (GeneralReleaseKey (StateT s m))

generalRelease :: GeneralReleaseKey (StateT s m) -> AllocationContext (StateT s m) ()

MonadAllocate m => MonadAllocate (StateT s m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (StateT s m) :: Type -> Type

type GeneralReleaseKey (StateT s m)

type AllocationException (StateT s m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (StateT s m)) (AllocationException (StateT s m)) () () a -> StateT s m (GeneralReleaseKey (StateT s m), a)

generalRegister :: (GeneralReleaseType (AllocationException (StateT s m)) () -> AllocationContext (StateT s m) ()) -> StateT s m (GeneralReleaseKey (StateT s m))

generalRelease :: GeneralReleaseKey (StateT s m) -> AllocationContext (StateT s m) ()

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

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (WriterT w m) :: Type -> Type

type GeneralReleaseKey (WriterT w m)

type AllocationException (WriterT w m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (WriterT w m)) (AllocationException (WriterT w m)) () () a -> WriterT w m (GeneralReleaseKey (WriterT w m), a)

generalRegister :: (GeneralReleaseType (AllocationException (WriterT w m)) () -> AllocationContext (WriterT w m) ()) -> WriterT w m (GeneralReleaseKey (WriterT w m))

generalRelease :: GeneralReleaseKey (WriterT w m) -> AllocationContext (WriterT w m) ()

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

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (WriterT w m) :: Type -> Type

type GeneralReleaseKey (WriterT w m)

type AllocationException (WriterT w m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (WriterT w m)) (AllocationException (WriterT w m)) () () a -> WriterT w m (GeneralReleaseKey (WriterT w m), a)

generalRegister :: (GeneralReleaseType (AllocationException (WriterT w m)) () -> AllocationContext (WriterT w m) ()) -> WriterT w m (GeneralReleaseKey (WriterT w m))

generalRelease :: GeneralReleaseKey (WriterT w m) -> AllocationContext (WriterT w m) ()

MonadAllocate m => MonadAllocate (ContT r m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (ContT r m) :: Type -> Type

type GeneralReleaseKey (ContT r m)

type AllocationException (ContT r m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (ContT r m)) (AllocationException (ContT r m)) () () a -> ContT r m (GeneralReleaseKey (ContT r m), a)

generalRegister :: (GeneralReleaseType (AllocationException (ContT r m)) () -> AllocationContext (ContT r m) ()) -> ContT r m (GeneralReleaseKey (ContT r m))

generalRelease :: GeneralReleaseKey (ContT r m) -> AllocationContext (ContT r m) ()

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

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (RWST r w s m) :: Type -> Type

type GeneralReleaseKey (RWST r w s m)

type AllocationException (RWST r w s m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (RWST r w s m)) (AllocationException (RWST r w s m)) () () a -> RWST r w s m (GeneralReleaseKey (RWST r w s m), a)

generalRegister :: (GeneralReleaseType (AllocationException (RWST r w s m)) () -> AllocationContext (RWST r w s m) ()) -> RWST r w s m (GeneralReleaseKey (RWST r w s m))

generalRelease :: GeneralReleaseKey (RWST r w s m) -> AllocationContext (RWST r w s m) ()

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

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (RWST r w s m) :: Type -> Type

type GeneralReleaseKey (RWST r w s m)

type AllocationException (RWST r w s m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (RWST r w s m)) (AllocationException (RWST r w s m)) () () a -> RWST r w s m (GeneralReleaseKey (RWST r w s m), a)

generalRegister :: (GeneralReleaseType (AllocationException (RWST r w s m)) () -> AllocationContext (RWST r w s m) ()) -> RWST r w s m (GeneralReleaseKey (RWST r w s m))

generalRelease :: GeneralReleaseKey (RWST r w s m) -> AllocationContext (RWST r w s m) ()

type MonadAllocateExceptable m = (MonadAllocate m, Exceptable (AllocationException m))

A MonadAllocate whose exception type can be projected into the Haskell exception hierarchy

newtype AllocateViaResource m a

A helper for DerivingVia a MonadAllocate instance for any MonadResource.

Constructors

AllocateViaResource (m a)

Instances

Applicative m => Applicative (AllocateViaResource m)

Defined in Control.Monad.Allocate

Methods

pure :: a -> AllocateViaResource m a

(<*>) :: AllocateViaResource m (a -> b) -> AllocateViaResource m a -> AllocateViaResource m b

liftA2 :: (a -> b -> c) -> AllocateViaResource m a -> AllocateViaResource m b -> AllocateViaResource m c

(*>) :: AllocateViaResource m a -> AllocateViaResource m b -> AllocateViaResource m b

(<*) :: AllocateViaResource m a -> AllocateViaResource m b -> AllocateViaResource m a

Functor m => Functor (AllocateViaResource m)

Defined in Control.Monad.Allocate

Methods

fmap :: (a -> b) -> AllocateViaResource m a -> AllocateViaResource m b

(<$) :: a -> AllocateViaResource m b -> AllocateViaResource m a

Monad m => Monad (AllocateViaResource m)

Defined in Control.Monad.Allocate

Methods

(>>=) :: AllocateViaResource m a -> (a -> AllocateViaResource m b) -> AllocateViaResource m b

(>>) :: AllocateViaResource m a -> AllocateViaResource m b -> AllocateViaResource m b

return :: a -> AllocateViaResource m a

MonadResource m => MonadAllocate (AllocateViaResource m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (AllocateViaResource m) :: Type -> Type

type GeneralReleaseKey (AllocateViaResource m)

type AllocationException (AllocateViaResource m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (AllocateViaResource m)) (AllocationException (AllocateViaResource m)) () () a -> AllocateViaResource m (GeneralReleaseKey (AllocateViaResource m), a)

generalRegister :: (GeneralReleaseType (AllocationException (AllocateViaResource m)) () -> AllocationContext (AllocateViaResource m) ()) -> AllocateViaResource m (GeneralReleaseKey (AllocateViaResource m))

generalRelease :: GeneralReleaseKey (AllocateViaResource m) -> AllocationContext (AllocateViaResource m) ()

type AllocationContext (AllocateViaResource m)

Defined in Control.Monad.Allocate

type AllocationContext (AllocateViaResource m) = IO

type AllocationException (AllocateViaResource m)

Defined in Control.Monad.Allocate

type AllocationException (AllocateViaResource m) = SomeException

type GeneralReleaseKey (AllocateViaResource m)

Defined in Control.Monad.Allocate

type GeneralReleaseKey (AllocateViaResource m) = ReleaseKey

newtype AllocateViaLift t m a

A helper for DerivingVia a MonadAllocate instance for any MonadTransformed MonadAllocate.

Constructors

AllocateViaLift (t m a)

Instances

MonadTrans t => MonadTrans (AllocateViaLift t)

Defined in Control.Monad.Allocate

Methods

lift :: Monad m => m a -> AllocateViaLift t m a

Applicative (t m) => Applicative (AllocateViaLift t m)

Defined in Control.Monad.Allocate

Methods

pure :: a -> AllocateViaLift t m a

(<*>) :: AllocateViaLift t m (a -> b) -> AllocateViaLift t m a -> AllocateViaLift t m b

liftA2 :: (a -> b -> c) -> AllocateViaLift t m a -> AllocateViaLift t m b -> AllocateViaLift t m c

(*>) :: AllocateViaLift t m a -> AllocateViaLift t m b -> AllocateViaLift t m b

(<*) :: AllocateViaLift t m a -> AllocateViaLift t m b -> AllocateViaLift t m a

Functor (t m) => Functor (AllocateViaLift t m)

Defined in Control.Monad.Allocate

Methods

fmap :: (a -> b) -> AllocateViaLift t m a -> AllocateViaLift t m b

(<$) :: a -> AllocateViaLift t m b -> AllocateViaLift t m a

Monad (t m) => Monad (AllocateViaLift t m)

Defined in Control.Monad.Allocate

Methods

(>>=) :: AllocateViaLift t m a -> (a -> AllocateViaLift t m b) -> AllocateViaLift t m b

(>>) :: AllocateViaLift t m a -> AllocateViaLift t m b -> AllocateViaLift t m b

return :: a -> AllocateViaLift t m a

(MonadAllocate m, MonadTrans t, Monad (t m)) => MonadAllocate (AllocateViaLift t m)

Defined in Control.Monad.Allocate

Associated Types

type AllocationContext (AllocateViaLift t m) :: Type -> Type

type GeneralReleaseKey (AllocateViaLift t m)

type AllocationException (AllocateViaLift t m)

Methods

generalAllocate :: GeneralAllocate (AllocationContext (AllocateViaLift t m)) (AllocationException (AllocateViaLift t m)) () () a -> AllocateViaLift t m (GeneralReleaseKey (AllocateViaLift t m), a)

generalRegister :: (GeneralReleaseType (AllocationException (AllocateViaLift t m)) () -> AllocationContext (AllocateViaLift t m) ()) -> AllocateViaLift t m (GeneralReleaseKey (AllocateViaLift t m))

generalRelease :: GeneralReleaseKey (AllocateViaLift t m) -> AllocationContext (AllocateViaLift t m) ()

type AllocationContext (AllocateViaLift t m)

Defined in Control.Monad.Allocate

type AllocationContext (AllocateViaLift t m) = AllocationContext m

type AllocationException (AllocateViaLift t m)

Defined in Control.Monad.Allocate

type AllocationException (AllocateViaLift t m) = AllocationException m

type GeneralReleaseKey (AllocateViaLift t m)

Defined in Control.Monad.Allocate

type GeneralReleaseKey (AllocateViaLift t m) = GeneralReleaseKey m