base-4.20.2.0: Core data structures and operations

Copyright | (c) The University of Glasgow 2001
License | BSD-style (see the file libraries/base/LICENSE)
Maintainer | libraries@haskell.org
Stability | stable
Portability | non-portable (uses Control.Monad.ST.Lazy)
Safe Haskell | Safe
Language | Haskell2010

Data.STRef.Lazy

Contents

- STRefs

Description

Mutable references in the lazy ST monad.

Synopsis

- data STRef s a
- newSTRef :: a -> ST s (STRef s a)
- readSTRef :: STRef s a -> ST s a
- writeSTRef :: STRef s a -> a -> ST s ()
- modifySTRef :: STRef s a -> (a -> a) -> ST s ()

# STRefs

data STRef s a Source #

a value of type `STRef s a` is a mutable variable in state thread `s`, containing a value of type `a`

    >>> :{
    runST (do
        ref <- newSTRef "hello"
        x <- readSTRef ref
        writeSTRef ref (x ++ "world")
        readSTRef ref )
    :}
    "helloworld"

#### Instances

Instances details

Eq (STRef s a) | Pointer equality. Since: base-2.1
Instance details Defined in GHC.Internal.STRef Methods (==) :: STRef s a -> STRef s a -> Bool Source # (/=) :: STRef s a -> STRef s a -> Bool Source #

newSTRef :: a -> ST s (STRef s a) Source #

readSTRef :: STRef s a -> ST s a Source #

writeSTRef :: STRef s a -> a -> ST s () Source #

modifySTRef :: STRef s a -> (a -> a) -> ST s () Source #