Copyright	(c) 2008-2020 Bertram Felgenhauer
License	MIT
Maintainer	Bertram Felgenhauer <int-e@gmx.de>
Stability	experimental
Portability	ghc
Safe Haskell	None
Language	Haskell2010

Data.IVar.Simple

Description

IVars are write-once variables.

Similarily to MVars, IVars can be either empty or filled. Once filled, they keep their value indefinitely - they are immutable.

Reading from an empty IVar will block until the IVar is filled. Because the value read will never change, this is a pure computation.

Synopsis

Documentation

A write-once (immutable) Variable

Instances

Eq (IVar a) Source #
Instance details Defined in Data.IVar.Simple Methods (==) :: IVar a -> IVar a -> Bool # (/=) :: IVar a -> IVar a -> Bool #

Create a new, empty IVar.

Create a new filled IVar.

This is slightly cheaper than creating a new IVar and then writing to it.

Returns the value of an IVar.

The evaluation will block until a value is written to the IVar if it has no value yet.

Try to read an IVar. Returns Nothing if it has no value yet.

write :: IVar a -> a -> IO () Source #

Writes a value to an IVar. Raises a BlockedIndefinitelyOnIVar exception if the variable already has a value.

Writes a value to an IVar. Returns True if successful, and False otherwise.

The thread has attempted to write to a full IVar.

Instances

Show BlockedIndefinitelyOnIVar Source #
Instance details Defined in Data.IVar.Simple Methods showsPrec :: Int -> BlockedIndefinitelyOnIVar -> ShowS # show :: BlockedIndefinitelyOnIVar -> String # showList :: [BlockedIndefinitelyOnIVar] -> ShowS #
Exception BlockedIndefinitelyOnIVar Source #
Instance details Defined in Data.IVar.Simple Methods toException :: BlockedIndefinitelyOnIVar -> SomeException # fromException :: SomeException -> Maybe BlockedIndefinitelyOnIVar # displayException :: BlockedIndefinitelyOnIVar -> String #