Control.Monad.Scoped.Internal

Internal module for Scoped, ScopedResource & co.

Only import this if you need to wrap an otherwise some still interface around resources

definitions of Scoped and ScopedResource and functions to work with them

newtype Scoped s m a

The Scoped monad that provides the possibility to safely scope the allocation of a resource

It is used to abstract over all of the CPS style withSomething functions, like withFile

Be sure to properly mask handlers if you are using UnsafeMkScoped. Use safe helper functions like registerHandler or bracketScoped where possible.

Constructors

UnsafeMkScoped

Fields

• unsafeRunScoped :: forall b. (a -> m b) -> m b

  Unsafely runs a scoped block. use scoped instead, otherwise resources might escape

Instances

MonadTrans (Scoped s :: (Type -> Type) -> Type -> Type)

Defined in Control.Monad.Scoped.Internal

Methods

lift :: Monad m => m a -> Scoped s m a

MonadFail m => MonadFail (Scoped s m)

Defined in Control.Monad.Scoped.Internal

Methods

fail :: String -> Scoped s m a

MonadIO m => MonadIO (Scoped s m)

You can perform IO in a scoped block, but it does not inherit its safety guarantees

Defined in Control.Monad.Scoped.Internal

Methods

liftIO :: IO a -> Scoped s m a

Alternative m => Alternative (Scoped s m)

Defined in Control.Monad.Scoped.Internal

Methods

empty :: Scoped s m a

(<|>) :: Scoped s m a -> Scoped s m a -> Scoped s m a

some :: Scoped s m a -> Scoped s m [a]

many :: Scoped s m a -> Scoped s m [a]

Applicative (Scoped s m)

Defined in Control.Monad.Scoped.Internal

Methods

pure :: a -> Scoped s m a

(<*>) :: Scoped s m (a -> b) -> Scoped s m a -> Scoped s m b

liftA2 :: (a -> b -> c) -> Scoped s m a -> Scoped s m b -> Scoped s m c

(*>) :: Scoped s m a -> Scoped s m b -> Scoped s m b

(<*) :: Scoped s m a -> Scoped s m b -> Scoped s m a

Functor (Scoped s m)

Defined in Control.Monad.Scoped.Internal

Methods

fmap :: (a -> b) -> Scoped s m a -> Scoped s m b

(<$) :: a -> Scoped s m b -> Scoped s m a

Monad (Scoped s m)

Defined in Control.Monad.Scoped.Internal

Methods

(>>=) :: Scoped s m a -> (a -> Scoped s m b) -> Scoped s m b

(>>) :: Scoped s m a -> Scoped s m b -> Scoped s m b

return :: a -> Scoped s m a

Alternative m => MonadPlus (Scoped s m)

Defined in Control.Monad.Scoped.Internal

Methods

mzero :: Scoped s m a

mplus :: Scoped s m a -> Scoped s m a -> Scoped s m a

newtype ScopedResource s a

A scoped resource with token s belonging to a Scoped block with the same token.

If you are creating a ScopedResource, make sure the resource is deallocated properly when the Scoped block is exited.

Constructors

UnsafeMkScopedResource

Fields

• unsafeUnwrapScopedResource :: a

  Unsafely runs a scoped resource. It forgets the scope of the resource and may now be escaped incorrectly

Instances

Show a => Show (ScopedResource s a)

Defined in Control.Monad.Scoped.Internal

Methods

showsPrec :: Int -> ScopedResource s a -> ShowS

show :: ScopedResource s a -> String

showList :: [ScopedResource s a] -> ShowS

Eq a => Eq (ScopedResource s a)

Defined in Control.Monad.Scoped.Internal

Methods

(==) :: ScopedResource s a -> ScopedResource s a -> Bool

(/=) :: ScopedResource s a -> ScopedResource s a -> Bool

Ord a => Ord (ScopedResource s a)

Defined in Control.Monad.Scoped.Internal

Methods

compare :: ScopedResource s a -> ScopedResource s a -> Ordering

(<) :: ScopedResource s a -> ScopedResource s a -> Bool

(<=) :: ScopedResource s a -> ScopedResource s a -> Bool

(>) :: ScopedResource s a -> ScopedResource s a -> Bool

(>=) :: ScopedResource s a -> ScopedResource s a -> Bool

max :: ScopedResource s a -> ScopedResource s a -> ScopedResource s a

min :: ScopedResource s a -> ScopedResource s a -> ScopedResource s a

scoped

Arguments

:: forall m a. Applicative m

=> (forall s. Scoped s m a)

the scoped computation to be run

-> m a

Run a Scoped block safely, making sure that none of the safely allocated resources can escape it, using the same trick as ST

All of the allocated resources will live until the end of the block is reached

registerHandler

Arguments

:: MonadUnliftIO m

=> m a

the handler to be registered

-> Scoped s m ()

Run a handler masked for async exception when the Scoped block ends

You can register a handler wherever in your Scoped block you want, but it will nonetheless be run in reverse order that the handlers have been registered, after the scoped block's actions have been finished

Helpers to create your own Scoped wrappers around resources

bracketScoped

Arguments

:: MonadUnliftIO m

=> m a

an action that allocates a resource of type a

-> (a -> m b)

an action that deallocates a resource of type a

-> Scoped s m (ScopedResource s a)

A wrapper around bracket to allocate a resource safely in a Scoped block

It returns a ScopedResource that belongs to the Scoped block it was allocated in