Movatterモバイル変換

{-# LANGUAGE Unsafe #-}{-# LANGUAGE NoImplicitPrelude, MagicHash, UnboxedTuples #-}{-# OPTIONS_HADDOCK hide #-}------------------------------------------------------------------------------- |-- Module      :  GHC.STRef-- Copyright   :  (c) The University of Glasgow, 1994-2002-- License     :  see libraries/base/LICENSE---- Maintainer  :  cvs-ghc@haskell.org-- Stability   :  internal-- Portability :  non-portable (GHC Extensions)---- References in the 'ST' monad.-------------------------------------------------------------------------------moduleGHC.STRef(STRef(..),newSTRef,readSTRef,writeSTRef)whereimportGHC.STimportGHC.Base-- $setup-- import PreludedataSTRefsa=STRef(MutVar#sa)-- ^ a value of type @STRef s a@ is a mutable variable in state thread @s@,-- containing a value of type @a@---- >>> :{-- runST (do--     ref <- newSTRef "hello"--     x <- readSTRef ref--     writeSTRef ref (x ++ "world")--     readSTRef ref )-- :}-- "helloworld"-- |Build a new 'STRef' in the current state threadnewSTRef::a->STs(STRefsa)newSTRefinit=ST$\s1#->casenewMutVar#inits1#of{(#s2#,var##)->(#s2#,STRefvar##)}-- |Read the value of an 'STRef'readSTRef::STRefsa->STsareadSTRef(STRefvar#)=ST$\s1#->readMutVar#var#s1#-- |Write a new value into an 'STRef'writeSTRef::STRefsa->a->STs()writeSTRef(STRefvar#)val=ST$\s1#->casewriteMutVar#var#vals1#of{s2#->(#s2#,()#)}-- | Pointer equality.---- @since 2.01instanceEq(STRefsa)whereSTRefv1#==STRefv2#=isTrue#(sameMutVar#v1#v2#)