Modulepolysemy-1.9.2.0Haskell2010

Polysemy.Resource

1 type
7 values

Packagepolysemy-1.9.2.0
Exports8
LanguageHaskell2010
LicenceBSD-3-Clause
SourceResource.hs

Effect

1 declaration

datadata Resource (m :: Type -> Type) a where

An effect capable of providing bracket semantics. Interpreters for this will successfully run the deallocation action even in the presence of other short-circuiting effects.

Constructors

Bracket :: m a -> (a -> m c) -> (a -> m b) -> Resource m a
Allocate a resource, use it, and clean it up afterwards.
BracketOnError :: m a -> (a -> m c) -> (a -> m b) -> Resource m a
Allocate a resource, use it, and clean it up afterwards if an error occurred.

Actions

5 declarations

valuebracket

:: Member Resource r
=> Sem r a
-> a -> Sem r c
-> a -> Sem r b
-> Sem r b

Allocate a resource, use it, and clean it up afterwards.

valuebracket_

:: Member Resource r
=> Sem r a
computation to run first
-> Sem r b
computation to run last (even if an exception was raised)
-> Sem r c
computation to run in-between
-> Sem r c

A variant of bracket where the return value from the first computation is not required.

cf. bracket and bracket_

valuebracketOnError

:: Member Resource r
=> Sem r a
-> a -> Sem r c
-> a -> Sem r b
-> Sem r b

Allocate a resource, use it, and clean it up afterwards if an error occurred.

valuefinally

:: Member Resource r
=> Sem r a
computation to run first
-> Sem r b
computation to run afterward (even if an exception was raised)
-> Sem r a

Like bracket, but for the simple case of one computation to run afterward.

valueonException

:: Member Resource r
=> Sem r a
computation to run first
-> Sem r b
computation to run afterward if an exception was raised
-> Sem r a

Like bracketOnError, but for the simple case of one computation to run afterward.

Interpretations

2 declarations

valuerunResource :: Sem (Resource ': r) a -> Sem r a

Run a Resource effect purely.

valueresourceToIOFinal :: Member (Final IO) r => Sem (Resource ': r) a -> Sem r a

Run a Resource effect in terms of bracket through final IO

Beware: Effects that aren't interpreted in terms of IO will have local state semantics in regards to Resource effects interpreted this way. See Final.