| Copyright | (c) Justin Bonnar 2011 Roman Leshchinskiy 2011-2012 |
|---|---|
| License | BSD-style |
| Maintainer | Roman Leshchinskiy <rl@cse.unsw.edu.au> |
| Portability | non-portable |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
Data.Primitive.MutVar
Description
Primitive boxed mutable variables. This is a generalization of
Data.IORef, Data.STRef and Data.STRef.Lazy to work in
any PrimMonad.
Synopsis
- data MutVar s a = MutVar (MutVar# s a)
- newMutVar :: PrimMonad m => a -> m (MutVar (PrimState m) a)
- readMutVar :: PrimMonad m => MutVar (PrimState m) a -> m a
- writeMutVar :: PrimMonad m => MutVar (PrimState m) a -> a -> m ()
- atomicModifyMutVar :: PrimMonad m => MutVar (PrimState m) a -> (a -> (a, b)) -> m b
- atomicModifyMutVar' :: PrimMonad m => MutVar (PrimState m) a -> (a -> (a, b)) -> m b
- modifyMutVar :: PrimMonad m => MutVar (PrimState m) a -> (a -> a) -> m ()
- modifyMutVar' :: PrimMonad m => MutVar (PrimState m) a -> (a -> a) -> m ()
Documentation
A MutVar behaves like a single-element mutable array associated
with a primitive state token.
newMutVar :: PrimMonad m => a -> m (MutVar (PrimState m) a) Source #
Create a new MutVar with the specified initial value.
writeMutVar :: PrimMonad m => MutVar (PrimState m) a -> a -> m () Source #
Write a new value into a MutVar.
atomicModifyMutVar :: PrimMonad m => MutVar (PrimState m) a -> (a -> (a, b)) -> m b Source #
Atomically mutate the contents of a MutVar.
This function is useful for using MutVar in a safe way in a multithreaded program.
If you only have one MutVar, then using atomicModifyMutVar to access and modify
it will prevent race conditions.
Extending the atomicity to multiple MutVars is problematic,
so if you need to do anything more complicated,
using MVar instead is a good idea.
atomicModifyMutVar does not apply the function strictly. This means if a program
calls atomicModifyMutVar many times, but seldom uses the value, thunks will pile up
in memory resulting in a space leak.
To avoid this problem, use atomicModifyMutVar' instead.
atomicModifyMutVar' :: PrimMonad m => MutVar (PrimState m) a -> (a -> (a, b)) -> m b Source #
Strict version of atomicModifyMutVar. This forces both the value stored
in the MutVar as well as the value returned.
modifyMutVar :: PrimMonad m => MutVar (PrimState m) a -> (a -> a) -> m () Source #
Mutate the contents of a MutVar.
modifyMutVar does not apply the function strictly. This means if a program
calls modifyMutVar many times, but seldom uses the value, thunks will pile up
in memory resulting in a space leak.
To avoid this problem, use modifyMutVar' instead.
modifyMutVar' :: PrimMonad m => MutVar (PrimState m) a -> (a -> a) -> m () Source #
Strict version of modifyMutVar.