Sophie: ghc-0:6.10.4-1mdv2010.0 i586

ghc-6.10.4-1mdv2010.0.i586.rpm

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>base-4.1.0.0: Basic libraries</TD
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>GHC.Conc</FONT
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><TR
><TD CLASS="infohead"
>Portability</TD
><TD CLASS="infoval"
>non-portable (GHC extensions)</TD
></TR
><TR
><TD CLASS="infohead"
>Stability</TD
><TD CLASS="infoval"
>internal</TD
></TR
><TR
><TD CLASS="infohead"
>Maintainer</TD
><TD CLASS="infoval"
>cvs-ghc@haskell.org</TD
></TR
></TABLE
></TD
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><TD CLASS="section4"
><B
>Contents</B
></TD
></TR
><TR
><TD
><DL
><DT
><A HREF="#1"
>Forking and suchlike
</A
></DT
><DT
><A HREF="#2"
>Waiting
</A
></DT
><DT
><A HREF="#3"
>MVars
</A
></DT
><DT
><A HREF="#4"
>TVars
</A
></DT
><DT
><A HREF="#5"
>Miscellaneous
</A
></DT
></DL
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="section1"
>Description</TD
></TR
><TR
><TD CLASS="doc"
>Basic concurrency stuff.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="section1"
>Synopsis</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A HREF="#t%3AThreadId"
>ThreadId</A
>  = <A HREF="#v%3AThreadId"
>ThreadId</A
> <A HREF="../ghc-prim/GHC-Prim.html#t%3AThreadId%23"
>ThreadId#</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AforkIO"
>forkIO</A
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AforkOnIO"
>forkOnIO</A
> :: <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AnumCapabilities"
>numCapabilities</A
> :: <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AchildHandler"
>childHandler</A
> :: <A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AmyThreadId"
>myThreadId</A
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AkillThread"
>killThread</A
> :: <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AthrowTo"
>throwTo</A
> :: <A HREF="Control-Exception-Base.html#t%3AException"
>Exception</A
> e =&gt; <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
> -&gt; e -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3Apar"
>par</A
> ::  a -&gt; b -&gt; b</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3Apseq"
>pseq</A
> ::  a -&gt; b -&gt; b</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3Ayield"
>yield</A
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AlabelThread"
>labelThread</A
> :: <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
> -&gt; <A HREF="Data-Char.html#t%3AString"
>String</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A HREF="#t%3AThreadStatus"
>ThreadStatus</A
>  </TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="decl"
>= <A HREF="#v%3AThreadRunning"
>ThreadRunning</A
></TD
></TR
><TR
><TD CLASS="decl"
>| <A HREF="#v%3AThreadFinished"
>ThreadFinished</A
></TD
></TR
><TR
><TD CLASS="decl"
>| <A HREF="#v%3AThreadBlocked"
>ThreadBlocked</A
> <A HREF="GHC-Conc.html#t%3ABlockReason"
>BlockReason</A
></TD
></TR
><TR
><TD CLASS="decl"
>| <A HREF="#v%3AThreadDied"
>ThreadDied</A
></TD
></TR
></TABLE
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A HREF="#t%3ABlockReason"
>BlockReason</A
>  </TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="decl"
>= <A HREF="#v%3ABlockedOnMVar"
>BlockedOnMVar</A
></TD
></TR
><TR
><TD CLASS="decl"
>| <A HREF="#v%3ABlockedOnBlackHole"
>BlockedOnBlackHole</A
></TD
></TR
><TR
><TD CLASS="decl"
>| <A HREF="#v%3ABlockedOnException"
>BlockedOnException</A
></TD
></TR
><TR
><TD CLASS="decl"
>| <A HREF="#v%3ABlockedOnSTM"
>BlockedOnSTM</A
></TD
></TR
><TR
><TD CLASS="decl"
>| <A HREF="#v%3ABlockedOnForeignCall"
>BlockedOnForeignCall</A
></TD
></TR
><TR
><TD CLASS="decl"
>| <A HREF="#v%3ABlockedOnOther"
>BlockedOnOther</A
></TD
></TR
></TABLE
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AthreadStatus"
>threadStatus</A
> :: <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="GHC-Conc.html#t%3AThreadStatus"
>ThreadStatus</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AthreadDelay"
>threadDelay</A
> :: <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AregisterDelay"
>registerDelay</A
> :: <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> <A HREF="../ghc-prim/GHC-Bool.html#t%3ABool"
>Bool</A
>)</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AthreadWaitRead"
>threadWaitRead</A
> :: <A HREF="System-Posix-Types.html#t%3AFd"
>Fd</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AthreadWaitWrite"
>threadWaitWrite</A
> :: <A HREF="System-Posix-Types.html#t%3AFd"
>Fd</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A HREF="#t%3AMVar"
>MVar</A
> a = <A HREF="#v%3AMVar"
>MVar</A
> (<A HREF="../ghc-prim/GHC-Prim.html#t%3AMVar%23"
>MVar#</A
> <A HREF="../ghc-prim/GHC-Prim.html#t%3ARealWorld"
>RealWorld</A
> a)</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AnewMVar"
>newMVar</A
> ::  a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a)</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AnewEmptyMVar"
>newEmptyMVar</A
> ::  <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a)</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AtakeMVar"
>takeMVar</A
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> a</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AputMVar"
>putMVar</A
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AtryTakeMVar"
>tryTakeMVar</A
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="Data-Maybe.html#t%3AMaybe"
>Maybe</A
> a)</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AtryPutMVar"
>tryPutMVar</A
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Bool.html#t%3ABool"
>Bool</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AisEmptyMVar"
>isEmptyMVar</A
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Bool.html#t%3ABool"
>Bool</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AaddMVarFinalizer"
>addMVarFinalizer</A
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>newtype</SPAN
>  <A HREF="#t%3ASTM"
>STM</A
> a = <A HREF="#v%3ASTM"
>STM</A
> (<A HREF="../ghc-prim/GHC-Prim.html#t%3AState%23"
>State#</A
> <A HREF="../ghc-prim/GHC-Prim.html#t%3ARealWorld"
>RealWorld</A
> -&gt; (#<A HREF="../ghc-prim/GHC-Prim.html#t%3AState%23"
>State#</A
> <A HREF="../ghc-prim/GHC-Prim.html#t%3ARealWorld"
>RealWorld</A
>, a#))</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3Aatomically"
>atomically</A
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> a</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3Aretry"
>retry</A
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AorElse"
>orElse</A
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AcatchSTM"
>catchSTM</A
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; (<A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a) -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AalwaysSucceeds"
>alwaysSucceeds</A
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3Aalways"
>always</A
> :: <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> <A HREF="../ghc-prim/GHC-Bool.html#t%3ABool"
>Bool</A
> -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A HREF="#t%3ATVar"
>TVar</A
> a = <A HREF="#v%3ATVar"
>TVar</A
> (<A HREF="../ghc-prim/GHC-Prim.html#t%3ATVar%23"
>TVar#</A
> <A HREF="../ghc-prim/GHC-Prim.html#t%3ARealWorld"
>RealWorld</A
> a)</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AnewTVar"
>newTVar</A
> ::  a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> (<A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> a)</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AnewTVarIO"
>newTVarIO</A
> ::  a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> a)</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AreadTVar"
>readTVar</A
> ::  <A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AwriteTVar"
>writeTVar</A
> ::  <A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> a -&gt; a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AunsafeIOToSTM"
>unsafeIOToSTM</A
> ::  <A HREF="System-IO.html#t%3AIO"
>IO</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>type</SPAN
> <A HREF="#t%3ASignal"
>Signal</A
> = <A HREF="Foreign-C-Types.html#t%3ACInt"
>CInt</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>type</SPAN
> <A HREF="#t%3AHandlerFun"
>HandlerFun</A
> = <A HREF="Foreign-ForeignPtr.html#t%3AForeignPtr"
>ForeignPtr</A
> <A HREF="Data-Word.html#t%3AWord8"
>Word8</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AsetHandler"
>setHandler</A
> :: <A HREF="GHC-Conc.html#t%3ASignal"
>Signal</A
> -&gt; <A HREF="Data-Maybe.html#t%3AMaybe"
>Maybe</A
> (<A HREF="GHC-Conc.html#t%3AHandlerFun"
>HandlerFun</A
>, <A HREF="Data-Dynamic.html#t%3ADynamic"
>Dynamic</A
>) -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="Data-Maybe.html#t%3AMaybe"
>Maybe</A
> (<A HREF="GHC-Conc.html#t%3AHandlerFun"
>HandlerFun</A
>, <A HREF="Data-Dynamic.html#t%3ADynamic"
>Dynamic</A
>))</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3ArunHandlers"
>runHandlers</A
> :: <A HREF="Foreign-Ptr.html#t%3APtr"
>Ptr</A
> <A HREF="Data-Word.html#t%3AWord8"
>Word8</A
> -&gt; <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AensureIOManagerIsRunning"
>ensureIOManagerIsRunning</A
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AsyncIOManager"
>syncIOManager</A
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AsetUncaughtExceptionHandler"
>setUncaughtExceptionHandler</A
> :: (<A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
>) -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AgetUncaughtExceptionHandler"
>getUncaughtExceptionHandler</A
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
>)</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AreportError"
>reportError</A
> ::  <A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> a</TD
></TR
><TR
><TD CLASS="s8"
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="#v%3AreportStackOverflow"
>reportStackOverflow</A
> ::  <A HREF="System-IO.html#t%3AIO"
>IO</A
> a</TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="section1"
>Documentation</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A NAME="t:ThreadId"
><A NAME="t%3AThreadId"
></A
></A
><B
>ThreadId</B
>  </TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="ndoc"
><P
>A <TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
> is an abstract type representing a handle to a thread.
<TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
> is an instance of <TT
><A HREF="Data-Eq.html#t%3AEq"
>Eq</A
></TT
>, <TT
><A HREF="Data-Ord.html#t%3AOrd"
>Ord</A
></TT
> and <TT
><A HREF="Text-Show.html#t%3AShow"
>Show</A
></TT
>, where
the <TT
><A HREF="Data-Ord.html#t%3AOrd"
>Ord</A
></TT
> instance implements an arbitrary total ordering over
<TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
>s. The <TT
><A HREF="Text-Show.html#t%3AShow"
>Show</A
></TT
> instance lets you convert an arbitrary-valued
<TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
> to string form; showing a <TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
> value is occasionally
useful when debugging or diagnosing the behaviour of a concurrent
program.
</P
><P
><EM
>Note</EM
>: in GHC, if you have a <TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
>, you essentially have
a pointer to the thread itself.  This means the thread itself can't be
garbage collected until you drop the <TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
>.
This misfeature will hopefully be corrected at a later date.
</P
><P
><EM
>Note</EM
>: Hugs does not provide any operations on other threads;
it defines <TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
> as a synonym for ().
</P
></TD
></TR
><TR
><TD CLASS="section4"
>Constructors</TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="arg"
><A NAME="v:ThreadId"
><A NAME="v%3AThreadId"
></A
></A
><B
>ThreadId</B
> <A HREF="../ghc-prim/GHC-Prim.html#t%3AThreadId%23"
>ThreadId#</A
></TD
><TD CLASS="rdoc"
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="section4"
><IMG SRC="minus.gif" CLASS="coll" ONCLICK="toggle(this,'i:ThreadId')" ALT="show/hide"
> Instances</TD
></TR
><TR
><TD CLASS="body"
><DIV ID="i:ThreadId" STYLE="display:block;"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="decl"
><A HREF="Data-Eq.html#t%3AEq"
>Eq</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Data-Ord.html#t%3AOrd"
>Ord</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Text-Show.html#t%3AShow"
>Show</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Data-Typeable.html#t%3ATypeable"
>Typeable</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="section1"
><A NAME="1"
><A NAME="1"
>Forking and suchlike
</A
></A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:forkIO"
><A NAME="v%3AforkIO"
></A
></A
><B
>forkIO</B
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
><TR
><TD CLASS="doc"
><P
>Sparks off a new thread to run the <TT
><A HREF="System-IO.html#t%3AIO"
>IO</A
></TT
> computation passed as the
first argument, and returns the <TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
> of the newly created
thread.
</P
><P
>The new thread will be a lightweight thread; if you want to use a foreign
library that uses thread-local storage, use Control.Concurrent.forkOS instead.
</P
><P
>GHC note: the new thread inherits the <EM
>blocked</EM
> state of the parent 
(see Control.Exception.block).
</P
><P
>The newly created thread has an exception handler that discards the
exceptions <TT
><A HREF="Control-Exception-Base.html#t%3ABlockedOnDeadMVar"
>BlockedOnDeadMVar</A
></TT
>, <TT
><A HREF="Control-Exception-Base.html#t%3ABlockedIndefinitely"
>BlockedIndefinitely</A
></TT
>, and
<TT
><A HREF="Control-Exception-Base.html#v%3AThreadKilled"
>ThreadKilled</A
></TT
>, and passes all other exceptions to the uncaught
exception handler (see <TT
><A HREF="GHC-Conc.html#v%3AsetUncaughtExceptionHandler"
>setUncaughtExceptionHandler</A
></TT
>).
</P
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:forkOnIO"
><A NAME="v%3AforkOnIO"
></A
></A
><B
>forkOnIO</B
> :: <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
><TR
><TD CLASS="doc"
><P
>Like <TT
><A HREF="GHC-Conc.html#v%3AforkIO"
>forkIO</A
></TT
>, but lets you specify on which CPU the thread is
created.  Unlike a <TT
><A HREF="GHC-Conc.html#v%3AforkIO"
>forkIO</A
></TT
> thread, a thread created by <TT
><A HREF="GHC-Conc.html#v%3AforkOnIO"
>forkOnIO</A
></TT
>
will stay on the same CPU for its entire lifetime (<TT
><A HREF="GHC-Conc.html#v%3AforkIO"
>forkIO</A
></TT
> threads
can migrate between CPUs according to the scheduling policy).
<TT
><A HREF="GHC-Conc.html#v%3AforkOnIO"
>forkOnIO</A
></TT
> is useful for overriding the scheduling policy when you
know in advance how best to distribute the threads.
</P
><P
>The <TT
><A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
></TT
> argument specifies the CPU number; it is interpreted modulo
<TT
><A HREF="GHC-Conc.html#v%3AnumCapabilities"
>numCapabilities</A
></TT
> (note that it actually specifies a capability number
rather than a CPU number, but to a first approximation the two are
equivalent).
</P
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:numCapabilities"
><A NAME="v%3AnumCapabilities"
></A
></A
><B
>numCapabilities</B
> :: <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
></TD
></TR
><TR
><TD CLASS="doc"
>the value passed to the <TT
>+RTS -N</TT
> flag.  This is the number of
 Haskell threads that can run truly simultaneously at any given
 time, and is typically set to the number of physical CPU cores on
 the machine.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:childHandler"
><A NAME="v%3AchildHandler"
></A
></A
><B
>childHandler</B
> :: <A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:myThreadId"
><A NAME="v%3AmyThreadId"
></A
></A
><B
>myThreadId</B
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TD
></TR
><TR
><TD CLASS="doc"
>Returns the <TT
><A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
></TT
> of the calling thread (GHC only).
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:killThread"
><A NAME="v%3AkillThread"
></A
></A
><B
>killThread</B
> :: <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
><P
><TT
><A HREF="GHC-Conc.html#v%3AkillThread"
>killThread</A
></TT
> terminates the given thread (GHC only).
Any work already done by the thread isn't
lost: the computation is suspended until required by another thread.
The memory used by the thread will be garbage collected if it isn't
referenced from anywhere.  The <TT
><A HREF="GHC-Conc.html#v%3AkillThread"
>killThread</A
></TT
> function is defined in
terms of <TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
>:
</P
><PRE
> killThread tid = throwTo tid ThreadKilled
</PRE
><P
>Killthread is a no-op if the target thread has already completed.
</P
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:throwTo"
><A NAME="v%3AthrowTo"
></A
></A
><B
>throwTo</B
> :: <A HREF="Control-Exception-Base.html#t%3AException"
>Exception</A
> e =&gt; <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
> -&gt; e -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
><P
><TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
> raises an arbitrary exception in the target thread (GHC only).
</P
><P
><TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
> does not return until the exception has been raised in the
target thread. 
The calling thread can thus be certain that the target
thread has received the exception.  This is a useful property to know
when dealing with race conditions: eg. if there are two threads that
can kill each other, it is guaranteed that only one of the threads
will get to kill the other.
</P
><P
>If the target thread is currently making a foreign call, then the
exception will not be raised (and hence <TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
> will not return)
until the call has completed.  This is the case regardless of whether
the call is inside a <TT
><A HREF="Control-Exception-Base.html#v%3Ablock"
>block</A
></TT
> or not.
</P
><P
>Important note: the behaviour of <TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
> differs from that described in
the paper &quot;Asynchronous exceptions in Haskell&quot;
(<A HREF="http://research.microsoft.com/~simonpj/Papers/asynch-exns.htm"
>http://research.microsoft.com/~simonpj/Papers/asynch-exns.htm</A
>).
In the paper, <TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
> is non-blocking; but the library implementation adopts
a more synchronous design in which <TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
> does not return until the exception
is received by the target thread.  The trade-off is discussed in Section 9 of the paper.
Like any blocking operation, <TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
> is therefore interruptible (see Section 5.3 of
the paper).
</P
><P
>There is currently no guarantee that the exception delivered by <TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
> will be
delivered at the first possible opportunity.  In particular, a thread may 
unblock and then re-block exceptions (using <TT
><A HREF="Control-Exception-Base.html#v%3Aunblock"
>unblock</A
></TT
> and <TT
><A HREF="Control-Exception-Base.html#v%3Ablock"
>block</A
></TT
>) without receiving
a pending <TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
>.  This is arguably undesirable behaviour.
</P
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:par"
><A NAME="v%3Apar"
></A
></A
><B
>par</B
> ::  a -&gt; b -&gt; b</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:pseq"
><A NAME="v%3Apseq"
></A
></A
><B
>pseq</B
> ::  a -&gt; b -&gt; b</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:yield"
><A NAME="v%3Ayield"
></A
></A
><B
>yield</B
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
>The <TT
><A HREF="GHC-Conc.html#v%3Ayield"
>yield</A
></TT
> action allows (forces, in a co-operative multitasking
 implementation) a context-switch to any other currently runnable
 threads (if any), and is occasionally useful when implementing
 concurrency abstractions.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:labelThread"
><A NAME="v%3AlabelThread"
></A
></A
><B
>labelThread</B
> :: <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
> -&gt; <A HREF="Data-Char.html#t%3AString"
>String</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
><P
><TT
><A HREF="GHC-Conc.html#v%3AlabelThread"
>labelThread</A
></TT
> stores a string as identifier for this thread if
you built a RTS with debugging support. This identifier will be used in
the debugging output to make distinction of different threads easier
(otherwise you only have the thread state object's address in the heap).
</P
><P
>Other applications like the graphical Concurrent Haskell Debugger
(<A HREF="http://www.informatik.uni-kiel.de/~fhu/chd/"
>http://www.informatik.uni-kiel.de/~fhu/chd/</A
>) may choose to overload
<TT
><A HREF="GHC-Conc.html#v%3AlabelThread"
>labelThread</A
></TT
> for their purposes as well.
</P
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A NAME="t:ThreadStatus"
><A NAME="t%3AThreadStatus"
></A
></A
><B
>ThreadStatus</B
>  </TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="ndoc"
>The current status of a thread
</TD
></TR
><TR
><TD CLASS="section4"
>Constructors</TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="arg"
><A NAME="v:ThreadRunning"
><A NAME="v%3AThreadRunning"
></A
></A
><B
>ThreadRunning</B
></TD
><TD CLASS="rdoc"
>the thread is currently runnable or running
</TD
></TR
><TR
><TD CLASS="arg"
><A NAME="v:ThreadFinished"
><A NAME="v%3AThreadFinished"
></A
></A
><B
>ThreadFinished</B
></TD
><TD CLASS="rdoc"
>the thread has finished
</TD
></TR
><TR
><TD CLASS="arg"
><A NAME="v:ThreadBlocked"
><A NAME="v%3AThreadBlocked"
></A
></A
><B
>ThreadBlocked</B
> <A HREF="GHC-Conc.html#t%3ABlockReason"
>BlockReason</A
></TD
><TD CLASS="rdoc"
>the thread is blocked on some resource
</TD
></TR
><TR
><TD CLASS="arg"
><A NAME="v:ThreadDied"
><A NAME="v%3AThreadDied"
></A
></A
><B
>ThreadDied</B
></TD
><TD CLASS="rdoc"
>the thread received an uncaught exception
</TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="section4"
><IMG SRC="minus.gif" CLASS="coll" ONCLICK="toggle(this,'i:ThreadStatus')" ALT="show/hide"
> Instances</TD
></TR
><TR
><TD CLASS="body"
><DIV ID="i:ThreadStatus" STYLE="display:block;"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="decl"
><A HREF="Data-Eq.html#t%3AEq"
>Eq</A
> <A HREF="GHC-Conc.html#t%3AThreadStatus"
>ThreadStatus</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Data-Ord.html#t%3AOrd"
>Ord</A
> <A HREF="GHC-Conc.html#t%3AThreadStatus"
>ThreadStatus</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Text-Show.html#t%3AShow"
>Show</A
> <A HREF="GHC-Conc.html#t%3AThreadStatus"
>ThreadStatus</A
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A NAME="t:BlockReason"
><A NAME="t%3ABlockReason"
></A
></A
><B
>BlockReason</B
>  </TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="section4"
>Constructors</TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="arg"
><A NAME="v:BlockedOnMVar"
><A NAME="v%3ABlockedOnMVar"
></A
></A
><B
>BlockedOnMVar</B
></TD
><TD CLASS="rdoc"
>blocked on on <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
>
</TD
></TR
><TR
><TD CLASS="arg"
><A NAME="v:BlockedOnBlackHole"
><A NAME="v%3ABlockedOnBlackHole"
></A
></A
><B
>BlockedOnBlackHole</B
></TD
><TD CLASS="rdoc"
>blocked on a computation in progress by another thread
</TD
></TR
><TR
><TD CLASS="arg"
><A NAME="v:BlockedOnException"
><A NAME="v%3ABlockedOnException"
></A
></A
><B
>BlockedOnException</B
></TD
><TD CLASS="rdoc"
>blocked in <TT
><A HREF="GHC-Conc.html#v%3AthrowTo"
>throwTo</A
></TT
>
</TD
></TR
><TR
><TD CLASS="arg"
><A NAME="v:BlockedOnSTM"
><A NAME="v%3ABlockedOnSTM"
></A
></A
><B
>BlockedOnSTM</B
></TD
><TD CLASS="rdoc"
>blocked in <TT
><A HREF="GHC-Conc.html#v%3Aretry"
>retry</A
></TT
> in an STM transaction
</TD
></TR
><TR
><TD CLASS="arg"
><A NAME="v:BlockedOnForeignCall"
><A NAME="v%3ABlockedOnForeignCall"
></A
></A
><B
>BlockedOnForeignCall</B
></TD
><TD CLASS="rdoc"
>currently in a foreign call
</TD
></TR
><TR
><TD CLASS="arg"
><A NAME="v:BlockedOnOther"
><A NAME="v%3ABlockedOnOther"
></A
></A
><B
>BlockedOnOther</B
></TD
><TD CLASS="rdoc"
>blocked on some other resource.  Without <TT
>-threaded</TT
>,
 I/O and <TT
><A HREF="GHC-Conc.html#v%3AthreadDelay"
>threadDelay</A
></TT
> show up as <TT
><A HREF="GHC-Conc.html#v%3ABlockedOnOther"
>BlockedOnOther</A
></TT
>, with <TT
>-threaded</TT
>
 they show up as <TT
><A HREF="GHC-Conc.html#v%3ABlockedOnMVar"
>BlockedOnMVar</A
></TT
>.
</TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="section4"
><IMG SRC="minus.gif" CLASS="coll" ONCLICK="toggle(this,'i:BlockReason')" ALT="show/hide"
> Instances</TD
></TR
><TR
><TD CLASS="body"
><DIV ID="i:BlockReason" STYLE="display:block;"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="decl"
><A HREF="Data-Eq.html#t%3AEq"
>Eq</A
> <A HREF="GHC-Conc.html#t%3ABlockReason"
>BlockReason</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Data-Ord.html#t%3AOrd"
>Ord</A
> <A HREF="GHC-Conc.html#t%3ABlockReason"
>BlockReason</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Text-Show.html#t%3AShow"
>Show</A
> <A HREF="GHC-Conc.html#t%3ABlockReason"
>BlockReason</A
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:threadStatus"
><A NAME="v%3AthreadStatus"
></A
></A
><B
>threadStatus</B
> :: <A HREF="GHC-Conc.html#t%3AThreadId"
>ThreadId</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="GHC-Conc.html#t%3AThreadStatus"
>ThreadStatus</A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="section1"
><A NAME="2"
><A NAME="2"
>Waiting
</A
></A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:threadDelay"
><A NAME="v%3AthreadDelay"
></A
></A
><B
>threadDelay</B
> :: <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
><P
>Suspends the current thread for a given number of microseconds
 (GHC only).
</P
><P
>There is no guarantee that the thread will be rescheduled promptly
 when the delay has expired, but the thread will never continue to
 run <EM
>earlier</EM
> than specified.
</P
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:registerDelay"
><A NAME="v%3AregisterDelay"
></A
></A
><B
>registerDelay</B
> :: <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> <A HREF="../ghc-prim/GHC-Bool.html#t%3ABool"
>Bool</A
>)</TD
></TR
><TR
><TD CLASS="doc"
>Set the value of returned TVar to True after a given number of
 microseconds. The caveats associated with threadDelay also apply.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:threadWaitRead"
><A NAME="v%3AthreadWaitRead"
></A
></A
><B
>threadWaitRead</B
> :: <A HREF="System-Posix-Types.html#t%3AFd"
>Fd</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
>Block the current thread until data is available to read on the
 given file descriptor (GHC only).
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:threadWaitWrite"
><A NAME="v%3AthreadWaitWrite"
></A
></A
><B
>threadWaitWrite</B
> :: <A HREF="System-Posix-Types.html#t%3AFd"
>Fd</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
>Block the current thread until data can be written to the
 given file descriptor (GHC only).
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="section1"
><A NAME="3"
><A NAME="3"
>MVars
</A
></A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A NAME="t:MVar"
><A NAME="t%3AMVar"
></A
></A
><B
>MVar</B
> a </TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="ndoc"
>An <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> (pronounced &quot;em-var&quot;) is a synchronising variable, used
for communication between concurrent threads.  It can be thought of
as a a box, which may be empty or full.
</TD
></TR
><TR
><TD CLASS="section4"
>Constructors</TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="arg"
><A NAME="v:MVar"
><A NAME="v%3AMVar"
></A
></A
><B
>MVar</B
> (<A HREF="../ghc-prim/GHC-Prim.html#t%3AMVar%23"
>MVar#</A
> <A HREF="../ghc-prim/GHC-Prim.html#t%3ARealWorld"
>RealWorld</A
> a)</TD
><TD CLASS="rdoc"
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="section4"
><IMG SRC="minus.gif" CLASS="coll" ONCLICK="toggle(this,'i:MVar')" ALT="show/hide"
> Instances</TD
></TR
><TR
><TD CLASS="body"
><DIV ID="i:MVar" STYLE="display:block;"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="decl"
><A HREF="Data-Typeable.html#t%3ATypeable1"
>Typeable1</A
> <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Data-Eq.html#t%3AEq"
>Eq</A
> (<A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a)</TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:newMVar"
><A NAME="v%3AnewMVar"
></A
></A
><B
>newMVar</B
> ::  a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a)</TD
></TR
><TR
><TD CLASS="doc"
>Create an <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> which contains the supplied value.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:newEmptyMVar"
><A NAME="v%3AnewEmptyMVar"
></A
></A
><B
>newEmptyMVar</B
> ::  <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a)</TD
></TR
><TR
><TD CLASS="doc"
>Create an <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> which is initially empty.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:takeMVar"
><A NAME="v%3AtakeMVar"
></A
></A
><B
>takeMVar</B
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> a</TD
></TR
><TR
><TD CLASS="doc"
><P
>Return the contents of the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
>.  If the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> is currently
 empty, <TT
><A HREF="GHC-Conc.html#v%3AtakeMVar"
>takeMVar</A
></TT
> will wait until it is full.  After a <TT
><A HREF="GHC-Conc.html#v%3AtakeMVar"
>takeMVar</A
></TT
>, 
 the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> is left empty.
</P
><P
>There are two further important properties of <TT
><A HREF="GHC-Conc.html#v%3AtakeMVar"
>takeMVar</A
></TT
>:
</P
><UL
><LI
> <TT
><A HREF="GHC-Conc.html#v%3AtakeMVar"
>takeMVar</A
></TT
> is single-wakeup.  That is, if there are multiple
     threads blocked in <TT
><A HREF="GHC-Conc.html#v%3AtakeMVar"
>takeMVar</A
></TT
>, and the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> becomes full,
     only one thread will be woken up.  The runtime guarantees that
     the woken thread completes its <TT
><A HREF="GHC-Conc.html#v%3AtakeMVar"
>takeMVar</A
></TT
> operation.
</LI
><LI
> When multiple threads are blocked on an <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
>, they are
     woken up in FIFO order.  This is useful for providing
     fairness properties of abstractions built using <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
>s.
</LI
></UL
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:putMVar"
><A NAME="v%3AputMVar"
></A
></A
><B
>putMVar</B
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
><P
>Put a value into an <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
>.  If the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> is currently full,
 <TT
><A HREF="GHC-Conc.html#v%3AputMVar"
>putMVar</A
></TT
> will wait until it becomes empty.
</P
><P
>There are two further important properties of <TT
><A HREF="GHC-Conc.html#v%3AputMVar"
>putMVar</A
></TT
>:
</P
><UL
><LI
> <TT
><A HREF="GHC-Conc.html#v%3AputMVar"
>putMVar</A
></TT
> is single-wakeup.  That is, if there are multiple
     threads blocked in <TT
><A HREF="GHC-Conc.html#v%3AputMVar"
>putMVar</A
></TT
>, and the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> becomes empty,
     only one thread will be woken up.  The runtime guarantees that
     the woken thread completes its <TT
><A HREF="GHC-Conc.html#v%3AputMVar"
>putMVar</A
></TT
> operation.
</LI
><LI
> When multiple threads are blocked on an <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
>, they are
     woken up in FIFO order.  This is useful for providing
     fairness properties of abstractions built using <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
>s.
</LI
></UL
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:tryTakeMVar"
><A NAME="v%3AtryTakeMVar"
></A
></A
><B
>tryTakeMVar</B
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="Data-Maybe.html#t%3AMaybe"
>Maybe</A
> a)</TD
></TR
><TR
><TD CLASS="doc"
>A non-blocking version of <TT
><A HREF="GHC-Conc.html#v%3AtakeMVar"
>takeMVar</A
></TT
>.  The <TT
><A HREF="GHC-Conc.html#v%3AtryTakeMVar"
>tryTakeMVar</A
></TT
> function
 returns immediately, with <TT
><A HREF="Data-Maybe.html#v%3ANothing"
>Nothing</A
></TT
> if the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> was empty, or
 <TT
><TT
><A HREF="Data-Maybe.html#v%3AJust"
>Just</A
></TT
> a</TT
> if the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> was full with contents <TT
>a</TT
>.  After <TT
><A HREF="GHC-Conc.html#v%3AtryTakeMVar"
>tryTakeMVar</A
></TT
>,
 the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> is left empty.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:tryPutMVar"
><A NAME="v%3AtryPutMVar"
></A
></A
><B
>tryPutMVar</B
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Bool.html#t%3ABool"
>Bool</A
></TD
></TR
><TR
><TD CLASS="doc"
>A non-blocking version of <TT
><A HREF="GHC-Conc.html#v%3AputMVar"
>putMVar</A
></TT
>.  The <TT
><A HREF="GHC-Conc.html#v%3AtryPutMVar"
>tryPutMVar</A
></TT
> function
 attempts to put the value <TT
>a</TT
> into the <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
>, returning <TT
><A HREF="../ghc-prim/GHC-Bool.html#v%3ATrue"
>True</A
></TT
> if
 it was successful, or <TT
><A HREF="../ghc-prim/GHC-Bool.html#v%3AFalse"
>False</A
></TT
> otherwise.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:isEmptyMVar"
><A NAME="v%3AisEmptyMVar"
></A
></A
><B
>isEmptyMVar</B
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Bool.html#t%3ABool"
>Bool</A
></TD
></TR
><TR
><TD CLASS="doc"
><P
>Check whether a given <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> is empty.
</P
><P
>Notice that the boolean value returned  is just a snapshot of
 the state of the MVar. By the time you get to react on its result,
 the MVar may have been filled (or emptied) - so be extremely
 careful when using this operation.   Use <TT
><A HREF="GHC-Conc.html#v%3AtryTakeMVar"
>tryTakeMVar</A
></TT
> instead if possible.
</P
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:addMVarFinalizer"
><A NAME="v%3AaddMVarFinalizer"
></A
></A
><B
>addMVarFinalizer</B
> ::  <A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
>Add a finalizer to an <TT
><A HREF="GHC-Conc.html#t%3AMVar"
>MVar</A
></TT
> (GHC only).  See <A HREF="Foreign-ForeignPtr.html"
>Foreign.ForeignPtr</A
> and
 <A HREF="System-Mem-Weak.html"
>System.Mem.Weak</A
> for more about finalizers.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="section1"
><A NAME="4"
><A NAME="4"
>TVars
</A
></A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>newtype</SPAN
>  <A NAME="t:STM"
><A NAME="t%3ASTM"
></A
></A
><B
>STM</B
> a </TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="ndoc"
>A monad supporting atomic memory transactions.
</TD
></TR
><TR
><TD CLASS="section4"
>Constructors</TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="arg"
><A NAME="v:STM"
><A NAME="v%3ASTM"
></A
></A
><B
>STM</B
> (<A HREF="../ghc-prim/GHC-Prim.html#t%3AState%23"
>State#</A
> <A HREF="../ghc-prim/GHC-Prim.html#t%3ARealWorld"
>RealWorld</A
> -&gt; (#<A HREF="../ghc-prim/GHC-Prim.html#t%3AState%23"
>State#</A
> <A HREF="../ghc-prim/GHC-Prim.html#t%3ARealWorld"
>RealWorld</A
>, a#))</TD
><TD CLASS="rdoc"
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="section4"
><IMG SRC="minus.gif" CLASS="coll" ONCLICK="toggle(this,'i:STM')" ALT="show/hide"
> Instances</TD
></TR
><TR
><TD CLASS="body"
><DIV ID="i:STM" STYLE="display:block;"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="decl"
><A HREF="Control-Monad.html#t%3AMonad"
>Monad</A
> <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Control-Monad.html#t%3AFunctor"
>Functor</A
> <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Data-Typeable.html#t%3ATypeable1"
>Typeable1</A
> <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:atomically"
><A NAME="v%3Aatomically"
></A
></A
><B
>atomically</B
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> a</TD
></TR
><TR
><TD CLASS="doc"
><P
>Perform a series of STM actions atomically.
</P
><P
>You cannot use <TT
><A HREF="GHC-Conc.html#v%3Aatomically"
>atomically</A
></TT
> inside an <TT
><A HREF="System-IO-Unsafe.html#v%3AunsafePerformIO"
>unsafePerformIO</A
></TT
> or <TT
><A HREF="System-IO-Unsafe.html#v%3AunsafeInterleaveIO"
>unsafeInterleaveIO</A
></TT
>. 
 Any attempt to do so will result in a runtime error.  (Reason: allowing
 this would effectively allow a transaction inside a transaction, depending
 on exactly when the thunk is evaluated.)
</P
><P
>However, see <TT
><A HREF="GHC-Conc.html#v%3AnewTVarIO"
>newTVarIO</A
></TT
>, which can be called inside <TT
><A HREF="System-IO-Unsafe.html#v%3AunsafePerformIO"
>unsafePerformIO</A
></TT
>,
 and which allows top-level TVars to be allocated.
</P
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:retry"
><A NAME="v%3Aretry"
></A
></A
><B
>retry</B
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="doc"
>Retry execution of the current memory transaction because it has seen
 values in TVars which mean that it should not continue (e.g. the TVars
 represent a shared buffer that is now empty).  The implementation may
 block the thread until one of the TVars that it has read from has been
 udpated. (GHC only)
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:orElse"
><A NAME="v%3AorElse"
></A
></A
><B
>orElse</B
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="doc"
>Compose two alternative STM actions (GHC only).  If the first action
 completes without retrying then it forms the result of the orElse.
 Otherwise, if the first action retries, then the second action is
 tried in its place.  If both actions retry then the orElse as a
 whole retries.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:catchSTM"
><A NAME="v%3AcatchSTM"
></A
></A
><B
>catchSTM</B
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; (<A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a) -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="doc"
>Exception handling within STM actions.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:alwaysSucceeds"
><A NAME="v%3AalwaysSucceeds"
></A
></A
><B
>alwaysSucceeds</B
> ::  <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
>alwaysSucceeds adds a new invariant that must be true when passed
 to alwaysSucceeds, at the end of the current transaction, and at
 the end of every subsequent transaction.  If it fails at any
 of those points then the transaction violating it is aborted
 and the exception raised by the invariant is propagated.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:always"
><A NAME="v%3Aalways"
></A
></A
><B
>always</B
> :: <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> <A HREF="../ghc-prim/GHC-Bool.html#t%3ABool"
>Bool</A
> -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
>always is a variant of alwaysSucceeds in which the invariant is
 expressed as an STM Bool action that must return True.  Returning
 False or raising an exception are both treated as invariant failures.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>data</SPAN
>  <A NAME="t:TVar"
><A NAME="t%3ATVar"
></A
></A
><B
>TVar</B
> a </TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0"
><TR
><TD CLASS="ndoc"
>Shared memory locations that support atomic memory transactions.
</TD
></TR
><TR
><TD CLASS="section4"
>Constructors</TD
></TR
><TR
><TD CLASS="body"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="arg"
><A NAME="v:TVar"
><A NAME="v%3ATVar"
></A
></A
><B
>TVar</B
> (<A HREF="../ghc-prim/GHC-Prim.html#t%3ATVar%23"
>TVar#</A
> <A HREF="../ghc-prim/GHC-Prim.html#t%3ARealWorld"
>RealWorld</A
> a)</TD
><TD CLASS="rdoc"
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="section4"
><IMG SRC="minus.gif" CLASS="coll" ONCLICK="toggle(this,'i:TVar')" ALT="show/hide"
> Instances</TD
></TR
><TR
><TD CLASS="body"
><DIV ID="i:TVar" STYLE="display:block;"
><TABLE CLASS="vanilla" CELLSPACING="1" CELLPADDING="0"
><TR
><TD CLASS="decl"
><A HREF="Data-Typeable.html#t%3ATypeable1"
>Typeable1</A
> <A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
></TD
></TR
><TR
><TD CLASS="decl"
><A HREF="Data-Eq.html#t%3AEq"
>Eq</A
> (<A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> a)</TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:newTVar"
><A NAME="v%3AnewTVar"
></A
></A
><B
>newTVar</B
> ::  a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> (<A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> a)</TD
></TR
><TR
><TD CLASS="doc"
>Create a new TVar holding a value supplied
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:newTVarIO"
><A NAME="v%3AnewTVarIO"
></A
></A
><B
>newTVarIO</B
> ::  a -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> a)</TD
></TR
><TR
><TD CLASS="doc"
><TT
>IO</TT
> version of <TT
><A HREF="GHC-Conc.html#v%3AnewTVar"
>newTVar</A
></TT
>.  This is useful for creating top-level
 <TT
><A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
></TT
>s using System.IO.Unsafe.unsafePerformIO, because using
 <TT
><A HREF="GHC-Conc.html#v%3Aatomically"
>atomically</A
></TT
> inside System.IO.Unsafe.unsafePerformIO isn't
 possible.
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:readTVar"
><A NAME="v%3AreadTVar"
></A
></A
><B
>readTVar</B
> ::  <A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="doc"
>Return the current value stored in a TVar
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:writeTVar"
><A NAME="v%3AwriteTVar"
></A
></A
><B
>writeTVar</B
> ::  <A HREF="GHC-Conc.html#t%3ATVar"
>TVar</A
> a -&gt; a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="doc"
>Write the supplied value into a TVar
</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:unsafeIOToSTM"
><A NAME="v%3AunsafeIOToSTM"
></A
></A
><B
>unsafeIOToSTM</B
> ::  <A HREF="System-IO.html#t%3AIO"
>IO</A
> a -&gt; <A HREF="GHC-Conc.html#t%3ASTM"
>STM</A
> a</TD
></TR
><TR
><TD CLASS="doc"
><P
>Unsafely performs IO in the STM monad.  Beware: this is a highly
 dangerous thing to do.  
</P
><UL
><LI
> The STM implementation will often run transactions multiple
     times, so you need to be prepared for this if your IO has any
     side effects.
</LI
><LI
> The STM implementation will abort transactions that are known to
     be invalid and need to be restarted.  This may happen in the middle
     of <TT
><A HREF="GHC-Conc.html#v%3AunsafeIOToSTM"
>unsafeIOToSTM</A
></TT
>, so make sure you don't acquire any resources
     that need releasing (exception handlers are ignored when aborting
     the transaction).  That includes doing any IO using Handles, for
     example.  Getting this wrong will probably lead to random deadlocks.
</LI
><LI
> The transaction may have seen an inconsistent view of memory when
     the IO runs.  Invariants that you expect to be true throughout
     your program may not be true inside a transaction, due to the
     way transactions are implemented.  Normally this wouldn't be visible
     to the programmer, but using <TT
><A HREF="GHC-Conc.html#v%3AunsafeIOToSTM"
>unsafeIOToSTM</A
></TT
> can expose it.
</LI
></UL
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="section1"
><A NAME="5"
><A NAME="5"
>Miscellaneous
</A
></A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>type</SPAN
> <A NAME="t:Signal"
><A NAME="t%3ASignal"
></A
></A
><B
>Signal</B
> = <A HREF="Foreign-C-Types.html#t%3ACInt"
>CInt</A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><SPAN CLASS="keyword"
>type</SPAN
> <A NAME="t:HandlerFun"
><A NAME="t%3AHandlerFun"
></A
></A
><B
>HandlerFun</B
> = <A HREF="Foreign-ForeignPtr.html#t%3AForeignPtr"
>ForeignPtr</A
> <A HREF="Data-Word.html#t%3AWord8"
>Word8</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:setHandler"
><A NAME="v%3AsetHandler"
></A
></A
><B
>setHandler</B
> :: <A HREF="GHC-Conc.html#t%3ASignal"
>Signal</A
> -&gt; <A HREF="Data-Maybe.html#t%3AMaybe"
>Maybe</A
> (<A HREF="GHC-Conc.html#t%3AHandlerFun"
>HandlerFun</A
>, <A HREF="Data-Dynamic.html#t%3ADynamic"
>Dynamic</A
>) -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="Data-Maybe.html#t%3AMaybe"
>Maybe</A
> (<A HREF="GHC-Conc.html#t%3AHandlerFun"
>HandlerFun</A
>, <A HREF="Data-Dynamic.html#t%3ADynamic"
>Dynamic</A
>))</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:runHandlers"
><A NAME="v%3ArunHandlers"
></A
></A
><B
>runHandlers</B
> :: <A HREF="Foreign-Ptr.html#t%3APtr"
>Ptr</A
> <A HREF="Data-Word.html#t%3AWord8"
>Word8</A
> -&gt; <A HREF="../ghc-prim/GHC-Types.html#t%3AInt"
>Int</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:ensureIOManagerIsRunning"
><A NAME="v%3AensureIOManagerIsRunning"
></A
></A
><B
>ensureIOManagerIsRunning</B
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:syncIOManager"
><A NAME="v%3AsyncIOManager"
></A
></A
><B
>syncIOManager</B
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:setUncaughtExceptionHandler"
><A NAME="v%3AsetUncaughtExceptionHandler"
></A
></A
><B
>setUncaughtExceptionHandler</B
> :: (<A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
>) -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
></TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:getUncaughtExceptionHandler"
><A NAME="v%3AgetUncaughtExceptionHandler"
></A
></A
><B
>getUncaughtExceptionHandler</B
> :: <A HREF="System-IO.html#t%3AIO"
>IO</A
> (<A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> <A HREF="../ghc-prim/GHC-Unit.html#t%3A%28%29"
>()</A
>)</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:reportError"
><A NAME="v%3AreportError"
></A
></A
><B
>reportError</B
> ::  <A HREF="Control-Exception-Base.html#t%3ASomeException"
>SomeException</A
> -&gt; <A HREF="System-IO.html#t%3AIO"
>IO</A
> a</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="decl"
><A NAME="v:reportStackOverflow"
><A NAME="v%3AreportStackOverflow"
></A
></A
><B
>reportStackOverflow</B
> ::  <A HREF="System-IO.html#t%3AIO"
>IO</A
> a</TD
></TR
><TR
><TD CLASS="s15"
></TD
></TR
><TR
><TD CLASS="botbar"
>Produced by <A HREF="http://www.haskell.org/haddock/"
>Haddock</A
> version 2.4.2</TD
></TR
></TABLE
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