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<title>GHC/IORef.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# OPTIONS_GHC -XNoImplicitPrelude -funbox-strict-fields #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-# OPTIONS_HADDOCK hide #-}</span>
<a name="line-3"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-4"></a><span class='hs-comment'>-- |</span>
<a name="line-5"></a><span class='hs-comment'>-- Module : GHC.IORef</span>
<a name="line-6"></a><span class='hs-comment'>-- Copyright : (c) The University of Glasgow 2008</span>
<a name="line-7"></a><span class='hs-comment'>-- License : see libraries/base/LICENSE</span>
<a name="line-8"></a><span class='hs-comment'>-- </span>
<a name="line-9"></a><span class='hs-comment'>-- Maintainer : cvs-ghc@haskell.org</span>
<a name="line-10"></a><span class='hs-comment'>-- Stability : internal</span>
<a name="line-11"></a><span class='hs-comment'>-- Portability : non-portable (GHC Extensions)</span>
<a name="line-12"></a><span class='hs-comment'>--</span>
<a name="line-13"></a><span class='hs-comment'>-- The IORef type</span>
<a name="line-14"></a><span class='hs-comment'>--</span>
<a name="line-15"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-16"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>IORef</span> <span class='hs-layout'>(</span>
<a name="line-17"></a> <span class='hs-conid'>IORef</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-18"></a> <span class='hs-varid'>newIORef</span><span class='hs-layout'>,</span> <span class='hs-varid'>readIORef</span><span class='hs-layout'>,</span> <span class='hs-varid'>writeIORef</span><span class='hs-layout'>,</span> <span class='hs-varid'>atomicModifyIORef</span>
<a name="line-19"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-20"></a>
<a name="line-21"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Base</span>
<a name="line-22"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>STRef</span>
<a name="line-23"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span>
<a name="line-24"></a>
<a name="line-25"></a><span class='hs-comment'>-- ---------------------------------------------------------------------------</span>
<a name="line-26"></a><span class='hs-comment'>-- IORefs</span>
<a name="line-27"></a>
<a name="line-28"></a><a name="IORef"></a><span class='hs-comment'>-- |A mutable variable in the 'IO' monad</span>
<a name="line-29"></a><a name="IORef"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>IORef</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>IORef</span> <span class='hs-layout'>(</span><span class='hs-conid'>STRef</span> <span class='hs-conid'>RealWorld</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-30"></a>
<a name="line-31"></a><span class='hs-comment'>-- explicit instance because Haddock can't figure out a derived one</span>
<a name="line-32"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Eq</span> <span class='hs-layout'>(</span><span class='hs-conid'>IORef</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-33"></a> <span class='hs-conid'>IORef</span> <span class='hs-varid'>x</span> <span class='hs-varop'>==</span> <span class='hs-conid'>IORef</span> <span class='hs-varid'>y</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span> <span class='hs-varop'>==</span> <span class='hs-varid'>y</span>
<a name="line-34"></a>
<a name="line-35"></a><a name="newIORef"></a><span class='hs-comment'>-- |Build a new 'IORef'</span>
<a name="line-36"></a><span class='hs-definition'>newIORef</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>IORef</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-37"></a><span class='hs-definition'>newIORef</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>stToIO</span> <span class='hs-layout'>(</span><span class='hs-varid'>newSTRef</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span> <span class='hs-varop'>>>=</span> <span class='hs-keyglyph'>\</span> <span class='hs-varid'>var</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>IORef</span> <span class='hs-varid'>var</span><span class='hs-layout'>)</span>
<a name="line-38"></a>
<a name="line-39"></a><a name="readIORef"></a><span class='hs-comment'>-- |Read the value of an 'IORef'</span>
<a name="line-40"></a><span class='hs-definition'>readIORef</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IORef</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-41"></a><span class='hs-definition'>readIORef</span> <span class='hs-layout'>(</span><span class='hs-conid'>IORef</span> <span class='hs-varid'>var</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>stToIO</span> <span class='hs-layout'>(</span><span class='hs-varid'>readSTRef</span> <span class='hs-varid'>var</span><span class='hs-layout'>)</span>
<a name="line-42"></a>
<a name="line-43"></a><a name="writeIORef"></a><span class='hs-comment'>-- |Write a new value into an 'IORef'</span>
<a name="line-44"></a><span class='hs-definition'>writeIORef</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IORef</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span>
<a name="line-45"></a><span class='hs-definition'>writeIORef</span> <span class='hs-layout'>(</span><span class='hs-conid'>IORef</span> <span class='hs-varid'>var</span><span class='hs-layout'>)</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>stToIO</span> <span class='hs-layout'>(</span><span class='hs-varid'>writeSTRef</span> <span class='hs-varid'>var</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span>
<a name="line-46"></a>
<a name="line-47"></a><a name="atomicModifyIORef"></a><span class='hs-definition'>atomicModifyIORef</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IORef</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span><span class='hs-varid'>b</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>b</span>
<a name="line-48"></a><span class='hs-definition'>atomicModifyIORef</span> <span class='hs-layout'>(</span><span class='hs-conid'>IORef</span> <span class='hs-layout'>(</span><span class='hs-conid'>STRef</span> <span class='hs-varid'>r</span><span class='hs-cpp'>#</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>IO</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>atomicModifyMutVar</span><span class='hs-cpp'>#</span> <span class='hs-varid'>r</span><span class='hs-cpp'>#</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span>
<a name="line-49"></a>
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