| Copyright | (c) 2016 Michael Walker |
|---|---|
| License | MIT |
| Maintainer | Michael Walker <mike@barrucadu.co.uk> |
| Stability | stable |
| Portability | portable |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
Control.Concurrent.Classy.MVar
Contents
Description
An MVar tt. It has two fundamental operations: putMVar
which fills an MVar if it is empty and blocks otherwise, and
takeMVar which empties an MVar if it is full and blocks
otherwise. They can be used in multiple different ways:
- As synchronized mutable variables,
- As channels, with
takeMVarandputMVaras receive and send, and - As a binary semaphore
MVar()takeMVarandputMVaras wait and signal.
Deviations: There is no Eq instance for MonadConc the
MVar type. Furthermore, the mkWeakMVar and addMVarFinalizer
functions are not provided. Finally, normal MVars have a fairness
guarantee, which dejafu does not currently make use of when
generating schedules to test, so your program may be tested with
unfair schedules.
Synopsis
- type family MVar m :: Type -> Type
- newEmptyMVar :: MonadConc m => m (MVar m a)
- newEmptyMVarN :: MonadConc m => String -> m (MVar m a)
- newMVar :: MonadConc m => a -> m (MVar m a)
- newMVarN :: MonadConc m => String -> a -> m (MVar m a)
- takeMVar :: MonadConc m => MVar m a -> m a
- putMVar :: MonadConc m => MVar m a -> a -> m ()
- readMVar :: MonadConc m => MVar m a -> m a
- swapMVar :: MonadConc m => MVar m a -> a -> m a
- tryTakeMVar :: MonadConc m => MVar m a -> m (Maybe a)
- tryPutMVar :: MonadConc m => MVar m a -> a -> m Bool
- isEmptyMVar :: MonadConc m => MVar m a -> m Bool
- withMVar :: MonadConc m => MVar m a -> (a -> m b) -> m b
- withMVarMasked :: MonadConc m => MVar m a -> (a -> m b) -> m b
- modifyMVar_ :: MonadConc m => MVar m a -> (a -> m a) -> m ()
- modifyMVar :: MonadConc m => MVar m a -> (a -> m (a, b)) -> m b
- modifyMVarMasked_ :: MonadConc m => MVar m a -> (a -> m a) -> m ()
- modifyMVarMasked :: MonadConc m => MVar m a -> (a -> m (a, b)) -> m b
MVars
type family MVar m :: Type -> Type Source #
The mutable reference type, like MVars. This may contain one
value at a time, attempting to read or take from an "empty"
MVar will block until it is full, and attempting to put to a
"full" MVar will block until it is empty.
Since: 1.0.0.0
Instances
| type MVar IO Source # | |
Defined in Control.Monad.Conc.Class | |
| type MVar (IsConc m) Source # | |
Defined in Control.Monad.Conc.Class | |
| type MVar (IdentityT m) Source # | |
Defined in Control.Monad.Conc.Class | |
| type MVar (ReaderT r m) Source # | |
Defined in Control.Monad.Conc.Class | |
| type MVar (StateT s m) Source # | |
Defined in Control.Monad.Conc.Class | |
| type MVar (StateT s m) Source # | |
Defined in Control.Monad.Conc.Class | |
| type MVar (WriterT w m) Source # | |
Defined in Control.Monad.Conc.Class | |
| type MVar (WriterT w m) Source # | |
Defined in Control.Monad.Conc.Class | |
| type MVar (RWST r w s m) Source # | |
Defined in Control.Monad.Conc.Class | |
| type MVar (RWST r w s m) Source # | |
Defined in Control.Monad.Conc.Class | |
newEmptyMVar :: MonadConc m => m (MVar m a) Source #
Create a new empty MVar.
newEmptyMVar = newEmptyMVarN ""
Since: 1.0.0.0
newEmptyMVarN :: MonadConc m => String -> m (MVar m a) Source #
Create a new empty MVar, but it is given a name which may be
used to present more useful debugging information.
newEmptyMVarN _ = newEmptyMVar
Since: 1.0.0.0
newMVar :: MonadConc m => a -> m (MVar m a) Source #
Create a new MVar containing a value.
Since: 1.0.0.0
newMVarN :: MonadConc m => String -> a -> m (MVar m a) Source #
Create a new MVar containing a value, but it is given a name
which may be used to present more useful debugging information.
Since: 1.0.0.0
takeMVar :: MonadConc m => MVar m a -> m a Source #
Take a value from a MVar. This "empties" the MVar,
allowing a new value to be put in. This will block if there is no
value in the MVar already, until one has been put.
Since: 1.0.0.0
putMVar :: MonadConc m => MVar m a -> a -> m () Source #
Put a value into a MVar. If there is already a value there,
this will block until that value has been taken, at which point
the value will be stored.
Since: 1.0.0.0
readMVar :: MonadConc m => MVar m a -> m a Source #
Block until a value is present in the MVar, and then return
it. This does not "remove" the value, multiple reads are
possible.
Since: 1.0.0.0
swapMVar :: MonadConc m => MVar m a -> a -> m a Source #
Swap the contents of a MVar, and return the value taken. This
function is atomic only if there are no other producers fro this
MVar.
Since: 1.0.0.0
isEmptyMVar :: MonadConc m => MVar m a -> m Bool Source #
Check if a MVar is empty.
The boolean value returned is just a snapshot of the state of the
MVar, it may have been emptied (or filled) by the time you
actually access it. Generally prefer tryPutMVar, tryTakeMVar,
and tryReadMVar.
Since: 1.0.0.0
withMVar :: MonadConc m => MVar m a -> (a -> m b) -> m b Source #
Operate on the contents of a MVar, replacing the contents after
finishing. This operation is exception-safe: it will replace the
original contents of the MVar if an exception is raised. However,
it is only atomic if there are no other producers for this MVar.
Since: 1.0.0.0
withMVarMasked :: MonadConc m => MVar m a -> (a -> m b) -> m b Source #
Like withMVar, but the IO action in the second argument is
executed with asynchronous exceptions masked.
Since: 1.0.0.0
modifyMVar_ :: MonadConc m => MVar m a -> (a -> m a) -> m () Source #
An exception-safe wrapper for modifying the contents of a MVar.
Like withMVar, modifyMVar will replace the original contents of
the MVar if an exception is raised during the operation. This
function is only atomic if there are no other producers for this
MVar.
Since: 1.0.0.0
modifyMVar :: MonadConc m => MVar m a -> (a -> m (a, b)) -> m b Source #
A slight variation on modifyMVar_ that allows a value to be
returned (b) in addition to the modified value of the MVar.
Since: 1.0.0.0
modifyMVarMasked_ :: MonadConc m => MVar m a -> (a -> m a) -> m () Source #
Like modifyMVar_, but the IO action in the second argument is
executed with asynchronous exceptions masked.
Since: 1.0.0.0
modifyMVarMasked :: MonadConc m => MVar m a -> (a -> m (a, b)) -> m b Source #
Like modifyMVar, but the IO action in the second argument is
executed with asynchronous exceptions masked.
Since: 1.0.0.0