Safe Haskell | None |
---|---|
Language | Haskell98 |
Guarding monadic computations with cleanup actions.
- class (Applicative μ, Monad μ) => MonadFinally μ where
- chainCleanups :: MonadFinally μ => [μ α] -> μ ()
- finallyMany :: MonadFinally μ => μ α -> [μ β] -> μ α
- onEscape :: MonadFinally μ => μ α -> μ β -> μ α
- onEscapeMany :: MonadFinally μ => μ α -> [μ β] -> μ α
- bracket_ :: MonadFinally μ => μ r -> μ β -> μ α -> μ α
- bracketOnEscape :: MonadFinally μ => μ r -> (r -> μ β) -> (r -> μ α) -> μ α
Documentation
class (Applicative μ, Monad μ) => MonadFinally μ where Source #
Class of monads that support guarding computations with cleanup actions.
finally' :: μ α -> (Maybe α -> μ β) -> μ (α, β) Source #
runs computation finally'
m fm
and then
finally :: μ α -> μ β -> μ α Source #
A simplified version of finally'
in which the cleanup action
does not care about the result of the main computation. The default
implementation is
finally
m =fmap
fst
.finally'
m .const
:: μ r | Acquire resource |
-> (r -> Maybe α -> μ β) | Release resource |
-> (r -> μ α) | Main computation |
-> μ (α, β) |
Safely acquire a resource and use it in a computation, releasing it even when the computation does not produce a result.
MonadFinally IO Source # | |
MonadFinally Identity Source # | |
MonadFinally μ => MonadFinally (MaybeT μ) Source # | |
MonadFinally μ => MonadFinally (ExceptT e μ) Source # | |
MonadFinally μ => MonadFinally (AbortT e μ) Source # | |
MonadFinally μ => MonadFinally (FinishT β μ) Source # | |
(MonadFinally μ, Monoid w) => MonadFinally (WriterT w μ) Source # | |
MonadFinally μ => MonadFinally (StateT s μ) Source # | |
(MonadFinally μ, Error e) => MonadFinally (ErrorT e μ) Source # | |
MonadFinally μ => MonadFinally (StateT s μ) Source # | |
(MonadFinally μ, Monoid w) => MonadFinally (WriterT w μ) Source # | |
(MonadFinally μ, Monoid w) => MonadFinally (AccumT w μ) Source # | |
MonadFinally μ => MonadFinally (ReaderT * r μ) Source # | |
(MonadFinally μ, Monoid w) => MonadFinally (RWST r w s μ) Source # | |
(MonadFinally μ, Monoid w) => MonadFinally (RWST r w s μ) Source # | |
chainCleanups :: MonadFinally μ => [μ α] -> μ () Source #
Run the provided list of cleanup actions sequentually, attempting to run the next action even if the previous one did not produce a result.
finallyMany :: MonadFinally μ => μ α -> [μ β] -> μ α Source #
A variant of finally
that combines multiple cleanup actions with
chainCleanups
.
onEscape :: MonadFinally μ => μ α -> μ β -> μ α Source #
runs computation onEscape
m cm
and then, if it did not produce
a result, runs computation c
.
onEscapeMany :: MonadFinally μ => μ α -> [μ β] -> μ α Source #
A variant of onEscape
that combines multiple cleanup actions with
chainCleanups
.
:: MonadFinally μ | |
=> μ r | Acquire resource |
-> μ β | Release resource |
-> μ α | Main computation |
-> μ α |
A variant of bracket
where acquired value is not needed (e.g. using
a static resource).
:: MonadFinally μ | |
=> μ r | Acquire resource |
-> (r -> μ β) | Release resource |
-> (r -> μ α) | Main computation |
-> μ α |
A variant of bracket
that releases the acquired resource only when
the main computation does not produce a value.