Control.Monad.Managed.Safe

This module is a safer subset of Control.Monad.Managed that only lets you unwrap the Managed type using runManaged. This enforces that you never leak acquired resources from a Managed computation.

In general, you should strive to propagate the Managed type as much as possible and use runManaged when you are done with acquired resources. However, there are legitimate circumstances where you want to return a value other than acquired resource from the bracketed computation, which requires using with.

This module is not the default because you can also use the Managed type for callback-based code that is completely unrelated to resources.

Managed

data Managed a

A managed resource that you acquire using with

Instances

Monad Managed

Methods

(>>=) :: Managed a -> (a -> Managed b) -> Managed b

(>>) :: Managed a -> Managed b -> Managed b

return :: a -> Managed a

fail :: String -> Managed a

Functor Managed

Methods

fmap :: (a -> b) -> Managed a -> Managed b

(<$) :: a -> Managed b -> Managed a

Applicative Managed

Methods

pure :: a -> Managed a

(<*>) :: Managed (a -> b) -> Managed a -> Managed b

liftA2 :: (a -> b -> c) -> Managed a -> Managed b -> Managed c

(*>) :: Managed a -> Managed b -> Managed b

(<*) :: Managed a -> Managed b -> Managed a

MonadIO Managed

Methods

liftIO :: IO a -> Managed a

MonadManaged Managed

Methods

using :: Managed a -> Managed a

Floating a => Floating (Managed a)

Methods

pi :: Managed a

exp :: Managed a -> Managed a

log :: Managed a -> Managed a

sqrt :: Managed a -> Managed a

(**) :: Managed a -> Managed a -> Managed a

logBase :: Managed a -> Managed a -> Managed a

sin :: Managed a -> Managed a

cos :: Managed a -> Managed a

tan :: Managed a -> Managed a

asin :: Managed a -> Managed a

acos :: Managed a -> Managed a

atan :: Managed a -> Managed a

sinh :: Managed a -> Managed a

cosh :: Managed a -> Managed a

tanh :: Managed a -> Managed a

asinh :: Managed a -> Managed a

acosh :: Managed a -> Managed a

atanh :: Managed a -> Managed a

log1p :: Managed a -> Managed a

expm1 :: Managed a -> Managed a

log1pexp :: Managed a -> Managed a

log1mexp :: Managed a -> Managed a

Fractional a => Fractional (Managed a)

Methods

(/) :: Managed a -> Managed a -> Managed a

recip :: Managed a -> Managed a

fromRational :: Rational -> Managed a

Num a => Num (Managed a)

Methods

(+) :: Managed a -> Managed a -> Managed a

(-) :: Managed a -> Managed a -> Managed a

(*) :: Managed a -> Managed a -> Managed a

negate :: Managed a -> Managed a

abs :: Managed a -> Managed a

signum :: Managed a -> Managed a

fromInteger :: Integer -> Managed a

Semigroup a => Semigroup (Managed a)

Methods

(<>) :: Managed a -> Managed a -> Managed a

sconcat :: NonEmpty (Managed a) -> Managed a

stimes :: Integral b => b -> Managed a -> Managed a

Monoid a => Monoid (Managed a)

Methods

mempty :: Managed a

mappend :: Managed a -> Managed a -> Managed a

mconcat :: [Managed a] -> Managed a

class MonadIO m => MonadManaged m where

You can embed a Managed action within any Monad that implements MonadManaged by using the using function

All instances must obey the following two laws:

using (return x) = return x

using (m >>= f) = using m >>= \x -> using (f x)

Minimal complete definition

using

Methods

using :: Managed a -> m a

Instances

MonadManaged Managed

Methods

using :: Managed a -> Managed a

MonadManaged m => MonadManaged (MaybeT m)

Methods

using :: Managed a -> MaybeT m a

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

Methods

using :: Managed a -> WriterT w m a

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

Methods

using :: Managed a -> WriterT w m a

MonadManaged m => MonadManaged (StateT s m)

Methods

using :: Managed a -> StateT s m a

MonadManaged m => MonadManaged (StateT s m)

Methods

using :: Managed a -> StateT s m a

MonadManaged m => MonadManaged (IdentityT * m)

Methods

using :: Managed a -> IdentityT * m a

MonadManaged m => MonadManaged (ExceptT e m)

Methods

using :: Managed a -> ExceptT e m a

MonadManaged m => MonadManaged (ReaderT * r m)

Methods

using :: Managed a -> ReaderT * r m a

MonadManaged m => MonadManaged (ContT * r m)

Methods

using :: Managed a -> ContT * r m a

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

Methods

using :: Managed a -> RWST r w s m a

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

Methods

using :: Managed a -> RWST r w s m a

managed :: (forall r. (a -> IO r) -> IO r) -> Managed a

Build a Managed value

managed_ :: (forall r. IO r -> IO r) -> Managed ()

Like managed but for resource-less operations.

runManaged :: Managed () -> IO ()

Run a Managed computation, enforcing that no acquired resources leak

Re-exports

Control.Monad.IO.Class re-exports MonadIO

module Control.Monad.IO.Class