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<pre><a name="line-1"></a><span class='hs-comment'>-------------------------</span>
<a name="line-2"></a><span class='hs-comment'>-- | </span>
<a name="line-3"></a><span class='hs-comment'>-- Module : Control.Exception</span>
<a name="line-4"></a><span class='hs-comment'>-- Copyright : (c) The University of Glasgow 2001</span>
<a name="line-5"></a><span class='hs-comment'>-- License : BSD-style (see the file LICENSE)</span>
<a name="line-6"></a><span class='hs-comment'>-- </span>
<a name="line-7"></a><span class='hs-comment'>-- Maintainer : libraries@haskell.org</span>
<a name="line-8"></a><span class='hs-comment'>-- Stability : experimental</span>
<a name="line-9"></a><span class='hs-comment'>-- Portability : non-portable (uses ExistentialQuantification and DeriveDataTypeable)</span>
<a name="line-10"></a><span class='hs-comment'>--</span>
<a name="line-11"></a><span class='hs-comment'>-- This module provides the extensible exceptions API for raising and catching both</span>
<a name="line-12"></a><span class='hs-comment'>-- built-in and user-defined exceptions.</span>
<a name="line-13"></a><span class='hs-comment'>-- </span>
<a name="line-14"></a><span class='hs-comment'>-- For newer versions of GHC (>=6.9), this package re-exports 'Control.Exception'. </span>
<a name="line-15"></a><span class='hs-comment'>-- Otherwise, it provides a compatibility layer around the previous version of the </span>
<a name="line-16"></a><span class='hs-comment'>-- extensions API.</span>
<a name="line-17"></a>
<a name="line-18"></a><span class='hs-cpp'>#ifdef USE_NEW_EXCEPTIONS</span>
<a name="line-19"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span><span class='hs-varop'>.</span><span class='hs-conid'>Extensible</span> <span class='hs-layout'>(</span><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span><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'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span><span class='hs-varid'>blocked</span><span class='hs-layout'>)</span>
<a name="line-22"></a>
<a name="line-23"></a><span class='hs-cpp'>#else</span>
<a name="line-24"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span><span class='hs-varop'>.</span><span class='hs-conid'>Extensible</span> <span class='hs-layout'>(</span>
<a name="line-25"></a> <span class='hs-comment'>-- * The Exception type</span>
<a name="line-26"></a> <span class='hs-conid'>SomeException</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-27"></a> <span class='hs-conid'>Exception</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-28"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>IOException</span><span class='hs-layout'>,</span>
<a name="line-29"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ArithException</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-30"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ArrayException</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-31"></a> <span class='hs-conid'>AssertionFailed</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-32"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>AsyncException</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-33"></a> <span class='hs-conid'>NonTermination</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-34"></a> <span class='hs-conid'>NestedAtomically</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-35"></a> <span class='hs-conid'>ExitCode</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-36"></a> <span class='hs-conid'>BlockedOnDeadMVar</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-37"></a> <span class='hs-conid'>BlockedIndefinitely</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-38"></a> <span class='hs-conid'>Deadlock</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-39"></a> <span class='hs-conid'>NoMethodError</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-40"></a> <span class='hs-conid'>PatternMatchFail</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-41"></a> <span class='hs-conid'>RecConError</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-42"></a> <span class='hs-conid'>RecSelError</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-43"></a> <span class='hs-conid'>RecUpdError</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-44"></a> <span class='hs-conid'>ErrorCall</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-45"></a>
<a name="line-46"></a> <span class='hs-comment'>-- * Throwing exceptions</span>
<a name="line-47"></a> <span class='hs-varid'>throwIO</span><span class='hs-layout'>,</span>
<a name="line-48"></a> <span class='hs-varid'>throw</span><span class='hs-layout'>,</span>
<a name="line-49"></a> <span class='hs-varid'>ioError</span><span class='hs-layout'>,</span>
<a name="line-50"></a> <span class='hs-varid'>throwTo</span><span class='hs-layout'>,</span>
<a name="line-51"></a> <span class='hs-comment'>-- * Catching Exceptions</span>
<a name="line-52"></a>
<a name="line-53"></a> <span class='hs-comment'>-- |There are several functions for catching and examining</span>
<a name="line-54"></a> <span class='hs-comment'>-- exceptions; all of them may only be used from within the</span>
<a name="line-55"></a> <span class='hs-comment'>-- 'IO' monad.</span>
<a name="line-56"></a>
<a name="line-57"></a> <span class='hs-comment'>-- ** The @catch@ functions</span>
<a name="line-58"></a> <span class='hs-varid'>catch</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: IO a -> (Exception -> IO a) -> IO a</span>
<a name="line-59"></a> <span class='hs-varid'>catches</span><span class='hs-layout'>,</span> <span class='hs-conid'>Handler</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-60"></a> <span class='hs-varid'>catchJust</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: (Exception -> Maybe b) -> IO a -> (b -> IO a) -> IO a</span>
<a name="line-61"></a>
<a name="line-62"></a> <span class='hs-comment'>-- ** The @handle@ functions</span>
<a name="line-63"></a> <span class='hs-varid'>handle</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: (Exception -> IO a) -> IO a -> IO a</span>
<a name="line-64"></a> <span class='hs-varid'>handleJust</span><span class='hs-layout'>,</span><span class='hs-comment'>-- :: (Exception -> Maybe b) -> (b -> IO a) -> IO a -> IO a</span>
<a name="line-65"></a>
<a name="line-66"></a> <span class='hs-comment'>-- ** The @try@ functions</span>
<a name="line-67"></a> <span class='hs-varid'>try</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: IO a -> IO (Either Exception a)</span>
<a name="line-68"></a> <span class='hs-varid'>tryJust</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: (Exception -> Maybe b) -> a -> IO (Either b a)</span>
<a name="line-69"></a> <span class='hs-varid'>onException</span><span class='hs-layout'>,</span>
<a name="line-70"></a>
<a name="line-71"></a> <span class='hs-comment'>-- ** The @evaluate@ function</span>
<a name="line-72"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>evaluate</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: a -> IO a</span>
<a name="line-73"></a>
<a name="line-74"></a> <span class='hs-comment'>-- ** The @mapException@ function</span>
<a name="line-75"></a> <span class='hs-varid'>mapException</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: (Exception -> Exception) -> a -> a</span>
<a name="line-76"></a>
<a name="line-77"></a> <span class='hs-comment'>-- * Asynchronous Exceptions</span>
<a name="line-78"></a>
<a name="line-79"></a> <span class='hs-comment'>-- $async</span>
<a name="line-80"></a>
<a name="line-81"></a> <span class='hs-comment'>-- ** Asynchronous exception control</span>
<a name="line-82"></a>
<a name="line-83"></a> <span class='hs-comment'>-- |The following two functions allow a thread to control delivery of</span>
<a name="line-84"></a> <span class='hs-comment'>-- asynchronous exceptions during a critical region.</span>
<a name="line-85"></a>
<a name="line-86"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>block</span><span class='hs-layout'>,</span>
<a name="line-87"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>unblock</span><span class='hs-layout'>,</span>
<a name="line-88"></a>
<a name="line-89"></a> <span class='hs-comment'>-- *** Applying @block@ to an exception handler</span>
<a name="line-90"></a>
<a name="line-91"></a> <span class='hs-comment'>-- $block_handler</span>
<a name="line-92"></a>
<a name="line-93"></a> <span class='hs-comment'>-- *** Interruptible operations</span>
<a name="line-94"></a>
<a name="line-95"></a> <span class='hs-comment'>-- $interruptible</span>
<a name="line-96"></a>
<a name="line-97"></a> <span class='hs-comment'>-- * Assertions</span>
<a name="line-98"></a>
<a name="line-99"></a> <span class='hs-varid'>assert</span><span class='hs-layout'>,</span>
<a name="line-100"></a>
<a name="line-101"></a> <span class='hs-comment'>-- * Utilities</span>
<a name="line-102"></a> <span class='hs-varid'>bracket</span><span class='hs-layout'>,</span>
<a name="line-103"></a> <span class='hs-varid'>bracket_</span><span class='hs-layout'>,</span>
<a name="line-104"></a> <span class='hs-varid'>bracketOnError</span><span class='hs-layout'>,</span>
<a name="line-105"></a> <span class='hs-varid'>finally</span>
<a name="line-106"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-107"></a>
<a name="line-108"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Prelude</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span><span class='hs-varid'>catch</span><span class='hs-layout'>)</span>
<a name="line-109"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Concurrent</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span><span class='hs-varid'>throwTo</span><span class='hs-layout'>)</span>
<a name="line-110"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>E</span>
<a name="line-111"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Dynamic</span>
<a name="line-112"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Typeable</span>
<a name="line-113"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>System</span><span class='hs-varop'>.</span><span class='hs-conid'>Exit</span>
<a name="line-114"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>System</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span><span class='hs-varop'>.</span><span class='hs-conid'>Unsafe</span><span class='hs-layout'>(</span><span class='hs-varid'>unsafePerformIO</span><span class='hs-layout'>)</span>
<a name="line-115"></a>
<a name="line-116"></a><a name="Exception"></a><span class='hs-keyword'>class</span> <span class='hs-layout'>(</span><span class='hs-conid'>Typeable</span> <span class='hs-varid'>e</span><span class='hs-layout'>,</span> <span class='hs-conid'>Show</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>where</span>
<a name="line-117"></a> <span class='hs-varid'>toException</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>SomeException</span>
<a name="line-118"></a> <span class='hs-varid'>fromException</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>SomeException</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-varid'>e</span>
<a name="line-119"></a>
<a name="line-120"></a> <span class='hs-varid'>toException</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SomeException</span>
<a name="line-121"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span>
<a name="line-122"></a>
<a name="line-123"></a><a name="SomeException"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>SomeException</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>forall</span> <span class='hs-varid'>e</span> <span class='hs-varop'>.</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span>
<a name="line-124"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-125"></a>
<a name="line-126"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>SomeException</span> <span class='hs-keyword'>where</span>
<a name="line-127"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-varid'>e</span>
<a name="line-128"></a>
<a name="line-129"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>SomeException</span> <span class='hs-keyword'>where</span>
<a name="line-130"></a> <span class='hs-varid'>toException</span> <span class='hs-varid'>se</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>se</span>
<a name="line-131"></a> <span class='hs-varid'>fromException</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span>
<a name="line-132"></a>
<a name="line-133"></a><a name="mkOldException"></a><span class='hs-definition'>mkOldException</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span>
<a name="line-134"></a><span class='hs-definition'>mkOldException</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>let</span> <span class='hs-varid'>e'</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-varid'>e</span>
<a name="line-135"></a> <span class='hs-keyword'>in</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>fromException</span> <span class='hs-varid'>e'</span> <span class='hs-keyword'>of</span>
<a name="line-136"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>e''</span> <span class='hs-keyglyph'>-></span> <span class='hs-comment'>-- If the exception is actually a legacy exception</span>
<a name="line-137"></a> <span class='hs-comment'>-- then throw it directly so the legacy functions</span>
<a name="line-138"></a> <span class='hs-comment'>-- catch it as they expect</span>
<a name="line-139"></a> <span class='hs-varid'>e''</span>
<a name="line-140"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-comment'>-- Otherwise, throw it as a dynamic</span>
<a name="line-141"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>DynException</span> <span class='hs-layout'>(</span><span class='hs-varid'>toDyn</span> <span class='hs-varid'>e'</span><span class='hs-layout'>)</span>
<a name="line-142"></a>
<a name="line-143"></a><a name="throw"></a><span class='hs-definition'>throw</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-144"></a><span class='hs-definition'>throw</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>throw</span> <span class='hs-layout'>(</span><span class='hs-varid'>mkOldException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span>
<a name="line-145"></a>
<a name="line-146"></a><a name="throwIO"></a><span class='hs-definition'>throwIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-147"></a><span class='hs-definition'>throwIO</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>throwIO</span> <span class='hs-layout'>(</span><span class='hs-varid'>mkOldException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span>
<a name="line-148"></a>
<a name="line-149"></a><a name="throwTo"></a><span class='hs-definition'>throwTo</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ThreadId</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span>
<a name="line-150"></a><span class='hs-definition'>throwTo</span> <span class='hs-varid'>tid</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>throwTo</span> <span class='hs-varid'>tid</span> <span class='hs-layout'>(</span><span class='hs-varid'>mkOldException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span>
<a name="line-151"></a>
<a name="line-152"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-153"></a><span class='hs-comment'>-- Catching exceptions</span>
<a name="line-154"></a>
<a name="line-155"></a><a name="catch"></a><span class='hs-comment'>-- |This is the simplest of the exception-catching functions. It</span>
<a name="line-156"></a><span class='hs-comment'>-- takes a single argument, runs it, and if an exception is raised</span>
<a name="line-157"></a><span class='hs-comment'>-- the \"handler\" is executed, with the value of the exception passed as an</span>
<a name="line-158"></a><span class='hs-comment'>-- argument. Otherwise, the result is returned as normal. For example:</span>
<a name="line-159"></a><span class='hs-comment'>--</span>
<a name="line-160"></a><span class='hs-comment'>-- > catch (openFile f ReadMode)</span>
<a name="line-161"></a><span class='hs-comment'>-- > (\e -> hPutStr stderr ("Couldn't open "++f++": " ++ show e))</span>
<a name="line-162"></a><span class='hs-comment'>--</span>
<a name="line-163"></a><span class='hs-comment'>-- For catching exceptions in pure (non-'IO') expressions, see the</span>
<a name="line-164"></a><span class='hs-comment'>-- function 'evaluate'.</span>
<a name="line-165"></a><span class='hs-comment'>--</span>
<a name="line-166"></a><span class='hs-comment'>-- Note that due to Haskell\'s unspecified evaluation order, an</span>
<a name="line-167"></a><span class='hs-comment'>-- expression may return one of several possible exceptions: consider</span>
<a name="line-168"></a><span class='hs-comment'>-- the expression @error \"urk\" + 1 \`div\` 0@. Does</span>
<a name="line-169"></a><span class='hs-comment'>-- 'catch' execute the handler passing</span>
<a name="line-170"></a><span class='hs-comment'>-- @ErrorCall \"urk\"@, or @ArithError DivideByZero@?</span>
<a name="line-171"></a><span class='hs-comment'>--</span>
<a name="line-172"></a><span class='hs-comment'>-- The answer is \"either\": 'catch' makes a</span>
<a name="line-173"></a><span class='hs-comment'>-- non-deterministic choice about which exception to catch. If you</span>
<a name="line-174"></a><span class='hs-comment'>-- call it again, you might get a different exception back. This is</span>
<a name="line-175"></a><span class='hs-comment'>-- ok, because 'catch' is an 'IO' computation.</span>
<a name="line-176"></a><span class='hs-comment'>--</span>
<a name="line-177"></a><span class='hs-comment'>-- Note that 'catch' catches all types of exceptions, and is generally</span>
<a name="line-178"></a><span class='hs-comment'>-- used for \"cleaning up\" before passing on the exception using</span>
<a name="line-179"></a><span class='hs-comment'>-- 'throwIO'. It is not good practice to discard the exception and</span>
<a name="line-180"></a><span class='hs-comment'>-- continue, without first checking the type of the exception (it</span>
<a name="line-181"></a><span class='hs-comment'>-- might be a 'ThreadKilled', for example). In this case it is usually better</span>
<a name="line-182"></a><span class='hs-comment'>-- to use 'catchJust' and select the kinds of exceptions to catch.</span>
<a name="line-183"></a><span class='hs-comment'>--</span>
<a name="line-184"></a><span class='hs-comment'>-- Also note that the "Prelude" also exports a function called</span>
<a name="line-185"></a><span class='hs-comment'>-- 'Prelude.catch' with a similar type to 'Control.Exception.catch',</span>
<a name="line-186"></a><span class='hs-comment'>-- except that the "Prelude" version only catches the IO and user</span>
<a name="line-187"></a><span class='hs-comment'>-- families of exceptions (as required by Haskell 98).</span>
<a name="line-188"></a><span class='hs-comment'>--</span>
<a name="line-189"></a><span class='hs-comment'>-- We recommend either hiding the "Prelude" version of 'Prelude.catch'</span>
<a name="line-190"></a><span class='hs-comment'>-- when importing "Control.Exception":</span>
<a name="line-191"></a><span class='hs-comment'>--</span>
<a name="line-192"></a><span class='hs-comment'>-- > import Prelude hiding (catch)</span>
<a name="line-193"></a><span class='hs-comment'>--</span>
<a name="line-194"></a><span class='hs-comment'>-- or importing "Control.Exception" qualified, to avoid name-clashes:</span>
<a name="line-195"></a><span class='hs-comment'>--</span>
<a name="line-196"></a><span class='hs-comment'>-- > import qualified Control.Exception as C</span>
<a name="line-197"></a><span class='hs-comment'>--</span>
<a name="line-198"></a><span class='hs-comment'>-- and then using @C.catch@</span>
<a name="line-199"></a><span class='hs-comment'>--</span>
<a name="line-200"></a><span class='hs-definition'>catch</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span>
<a name="line-201"></a> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-comment'>-- ^ The computation to run</span>
<a name="line-202"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ Handler to invoke if an exception is raised</span>
<a name="line-203"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-204"></a><span class='hs-definition'>catch</span> <span class='hs-varid'>io</span> <span class='hs-varid'>poly_handler</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>io</span> <span class='hs-varop'>`</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>catch</span><span class='hs-varop'>`</span> <span class='hs-varid'>handler'</span>
<a name="line-205"></a> <span class='hs-keyword'>where</span>
<a name="line-206"></a> <span class='hs-comment'>-- First look for "new style" exceptions, which are thrown</span>
<a name="line-207"></a> <span class='hs-comment'>-- as E.DynException (SomeException e)</span>
<a name="line-208"></a>
<a name="line-209"></a> <span class='hs-comment'>-- needs scoped TVs: handler' :: E.Exception -> IO a </span>
<a name="line-210"></a> <span class='hs-varid'>handler'</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-211"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>DynException</span> <span class='hs-varid'>dyn</span> <span class='hs-keyglyph'>-></span>
<a name="line-212"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>fromDynamic</span> <span class='hs-varid'>dyn</span> <span class='hs-keyword'>of</span>
<a name="line-213"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>se</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-214"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>fromException</span> <span class='hs-varid'>se</span> <span class='hs-keyword'>of</span>
<a name="line-215"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>e'</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>poly_handler</span> <span class='hs-varid'>e'</span>
<a name="line-216"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>throw</span> <span class='hs-varid'>e</span>
<a name="line-217"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>try_old</span> <span class='hs-varid'>e</span>
<a name="line-218"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>try_old</span> <span class='hs-varid'>e</span>
<a name="line-219"></a>
<a name="line-220"></a> <span class='hs-comment'>-- If it's a legacy exception (E.Exception or one of the</span>
<a name="line-221"></a> <span class='hs-comment'>-- types that make up E.Exception), check for a handler than</span>
<a name="line-222"></a> <span class='hs-comment'>-- can handle them:</span>
<a name="line-223"></a>
<a name="line-224"></a> <span class='hs-comment'>-- needs scoped TVs: try_old :: E.Exception -> IO a</span>
<a name="line-225"></a> <span class='hs-varid'>try_old</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-varid'>toException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyword'>of</span>
<a name="line-226"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>e'</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>poly_handler</span> <span class='hs-varid'>e'</span>
<a name="line-227"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>throw</span> <span class='hs-varid'>e</span>
<a name="line-228"></a>
<a name="line-229"></a>
<a name="line-230"></a><a name="bracket"></a><span class='hs-comment'>-- | When you want to acquire a resource, do some work with it, and</span>
<a name="line-231"></a><span class='hs-comment'>-- then release the resource, it is a good idea to use 'bracket',</span>
<a name="line-232"></a><span class='hs-comment'>-- because 'bracket' will install the necessary exception handler to</span>
<a name="line-233"></a><span class='hs-comment'>-- release the resource in the event that an exception is raised</span>
<a name="line-234"></a><span class='hs-comment'>-- during the computation. If an exception is raised, then 'bracket' will</span>
<a name="line-235"></a><span class='hs-comment'>-- re-raise the exception (after performing the release).</span>
<a name="line-236"></a><span class='hs-comment'>--</span>
<a name="line-237"></a><span class='hs-comment'>-- A common example is opening a file:</span>
<a name="line-238"></a><span class='hs-comment'>--</span>
<a name="line-239"></a><span class='hs-comment'>-- > bracket</span>
<a name="line-240"></a><span class='hs-comment'>-- > (openFile "filename" ReadMode)</span>
<a name="line-241"></a><span class='hs-comment'>-- > (hClose)</span>
<a name="line-242"></a><span class='hs-comment'>-- > (\handle -> do { ... })</span>
<a name="line-243"></a><span class='hs-comment'>--</span>
<a name="line-244"></a><span class='hs-comment'>-- The arguments to 'bracket' are in this order so that we can partially apply</span>
<a name="line-245"></a><span class='hs-comment'>-- it, e.g.:</span>
<a name="line-246"></a><span class='hs-comment'>--</span>
<a name="line-247"></a><span class='hs-comment'>-- > withFile name mode = bracket (openFile name mode) hClose</span>
<a name="line-248"></a><span class='hs-comment'>--</span>
<a name="line-249"></a><span class='hs-definition'>bracket</span>
<a name="line-250"></a> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-comment'>-- ^ computation to run first (\"acquire resource\")</span>
<a name="line-251"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ computation to run last (\"release resource\")</span>
<a name="line-252"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ computation to run in-between</span>
<a name="line-253"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>c</span> <span class='hs-comment'>-- returns the value from the in-between computation</span>
<a name="line-254"></a><span class='hs-definition'>bracket</span> <span class='hs-varid'>before</span> <span class='hs-varid'>after</span> <span class='hs-varid'>thing</span> <span class='hs-keyglyph'>=</span>
<a name="line-255"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>block</span> <span class='hs-layout'>(</span><span class='hs-keyword'>do</span>
<a name="line-256"></a> <span class='hs-varid'>a</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>before</span>
<a name="line-257"></a> <span class='hs-varid'>r</span> <span class='hs-keyglyph'><-</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>unblock</span> <span class='hs-layout'>(</span><span class='hs-varid'>thing</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varop'>`onException`</span> <span class='hs-varid'>after</span> <span class='hs-varid'>a</span>
<a name="line-258"></a> <span class='hs-varid'>after</span> <span class='hs-varid'>a</span>
<a name="line-259"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>r</span>
<a name="line-260"></a> <span class='hs-layout'>)</span>
<a name="line-261"></a>
<a name="line-262"></a><a name="onException"></a><span class='hs-definition'>onException</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-263"></a><span class='hs-definition'>onException</span> <span class='hs-varid'>io</span> <span class='hs-varid'>what</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>io</span> <span class='hs-varop'>`catch`</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span> <span class='hs-varid'>what</span>
<a name="line-264"></a> <span class='hs-varid'>throw</span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>SomeException</span><span class='hs-layout'>)</span>
<a name="line-265"></a>
<a name="line-266"></a><a name="block"></a><span class='hs-definition'>block</span><span class='hs-layout'>,</span> <span class='hs-varid'>unblock</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</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-267"></a><span class='hs-definition'>block</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>block</span>
<a name="line-268"></a><a name="unblock"></a><span class='hs-definition'>unblock</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>unblock</span>
<a name="line-269"></a>
<a name="line-270"></a><a name="finally"></a><span class='hs-comment'>-- | A specialised variant of 'bracket' with just a computation to run</span>
<a name="line-271"></a><span class='hs-comment'>-- afterward.</span>
<a name="line-272"></a><span class='hs-comment'>--</span>
<a name="line-273"></a><span class='hs-definition'>finally</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-comment'>-- ^ computation to run first</span>
<a name="line-274"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>b</span> <span class='hs-comment'>-- ^ computation to run afterward (even if an exception</span>
<a name="line-275"></a> <span class='hs-comment'>-- was raised)</span>
<a name="line-276"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-comment'>-- returns the value from the first computation</span>
<a name="line-277"></a><a name="finally"></a><span class='hs-definition'>a</span> <span class='hs-varop'>`finally`</span> <span class='hs-varid'>sequel</span> <span class='hs-keyglyph'>=</span>
<a name="line-278"></a> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>block</span> <span class='hs-layout'>(</span><span class='hs-keyword'>do</span>
<a name="line-279"></a> <span class='hs-varid'>r</span> <span class='hs-keyglyph'><-</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>unblock</span> <span class='hs-varid'>a</span> <span class='hs-varop'>`onException`</span> <span class='hs-varid'>sequel</span>
<a name="line-280"></a> <span class='hs-varid'>sequel</span>
<a name="line-281"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>r</span>
<a name="line-282"></a> <span class='hs-layout'>)</span>
<a name="line-283"></a>
<a name="line-284"></a><a name="bracket_"></a><span class='hs-comment'>-- | A variant of 'bracket' where the return value from the first computation</span>
<a name="line-285"></a><span class='hs-comment'>-- is not required.</span>
<a name="line-286"></a><span class='hs-definition'>bracket_</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>c</span>
<a name="line-287"></a><span class='hs-definition'>bracket_</span> <span class='hs-varid'>before</span> <span class='hs-varid'>after</span> <span class='hs-varid'>thing</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>bracket</span> <span class='hs-varid'>before</span> <span class='hs-layout'>(</span><span class='hs-varid'>const</span> <span class='hs-varid'>after</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>const</span> <span class='hs-varid'>thing</span><span class='hs-layout'>)</span>
<a name="line-288"></a>
<a name="line-289"></a><a name="bracketOnError"></a><span class='hs-comment'>-- | Like bracket, but only performs the final action if there was an</span>
<a name="line-290"></a><span class='hs-comment'>-- exception raised by the in-between computation.</span>
<a name="line-291"></a><span class='hs-definition'>bracketOnError</span>
<a name="line-292"></a> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-comment'>-- ^ computation to run first (\"acquire resource\")</span>
<a name="line-293"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ computation to run last (\"release resource\")</span>
<a name="line-294"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ computation to run in-between</span>
<a name="line-295"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>c</span> <span class='hs-comment'>-- returns the value from the in-between computation</span>
<a name="line-296"></a><span class='hs-definition'>bracketOnError</span> <span class='hs-varid'>before</span> <span class='hs-varid'>after</span> <span class='hs-varid'>thing</span> <span class='hs-keyglyph'>=</span>
<a name="line-297"></a> <span class='hs-varid'>block</span> <span class='hs-layout'>(</span><span class='hs-keyword'>do</span>
<a name="line-298"></a> <span class='hs-varid'>a</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>before</span>
<a name="line-299"></a> <span class='hs-varid'>unblock</span> <span class='hs-layout'>(</span><span class='hs-varid'>thing</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varop'>`onException`</span> <span class='hs-varid'>after</span> <span class='hs-varid'>a</span>
<a name="line-300"></a> <span class='hs-layout'>)</span>
<a name="line-301"></a>
<a name="line-302"></a><a name="assert"></a><span class='hs-definition'>assert</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Bool</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-303"></a><span class='hs-definition'>assert</span> <span class='hs-conid'>True</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span>
<a name="line-304"></a><span class='hs-definition'>assert</span> <span class='hs-conid'>False</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>throw</span> <span class='hs-layout'>(</span><span class='hs-conid'>AssertionFailed</span> <span class='hs-str'>""</span><span class='hs-layout'>)</span>
<a name="line-305"></a>
<a name="line-306"></a><a name="catchJust"></a><span class='hs-comment'>-- | The function 'catchJust' is like 'catch', but it takes an extra</span>
<a name="line-307"></a><span class='hs-comment'>-- argument which is an /exception predicate/, a function which</span>
<a name="line-308"></a><span class='hs-comment'>-- selects which type of exceptions we\'re interested in.</span>
<a name="line-309"></a><span class='hs-comment'>--</span>
<a name="line-310"></a><span class='hs-comment'>-- > result <- catchJust errorCalls thing_to_try handler</span>
<a name="line-311"></a><span class='hs-comment'>--</span>
<a name="line-312"></a><span class='hs-comment'>-- Any other exceptions which are not matched by the predicate</span>
<a name="line-313"></a><span class='hs-comment'>-- are re-raised, and may be caught by an enclosing</span>
<a name="line-314"></a><span class='hs-comment'>-- 'catch' or 'catchJust'.</span>
<a name="line-315"></a><span class='hs-definition'>catchJust</span>
<a name="line-316"></a> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span>
<a name="line-317"></a> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ Predicate to select exceptions</span>
<a name="line-318"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-comment'>-- ^ Computation to run</span>
<a name="line-319"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-comment'>-- ^ Handler</span>
<a name="line-320"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-321"></a><span class='hs-definition'>catchJust</span> <span class='hs-varid'>p</span> <span class='hs-varid'>a</span> <span class='hs-varid'>handler</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>catch</span> <span class='hs-varid'>a</span> <span class='hs-varid'>handler'</span>
<a name="line-322"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>handler'</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>p</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-323"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>throw</span> <span class='hs-varid'>e</span>
<a name="line-324"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>handler</span> <span class='hs-varid'>b</span>
<a name="line-325"></a>
<a name="line-326"></a><a name="handle"></a><span class='hs-comment'>-- | A version of 'catch' with the arguments swapped around; useful in</span>
<a name="line-327"></a><span class='hs-comment'>-- situations where the code for the handler is shorter. For example:</span>
<a name="line-328"></a><span class='hs-comment'>--</span>
<a name="line-329"></a><span class='hs-comment'>-- > do handle (\e -> exitWith (ExitFailure 1)) $</span>
<a name="line-330"></a><span class='hs-comment'>-- > ...</span>
<a name="line-331"></a><span class='hs-definition'>handle</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</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-332"></a><span class='hs-definition'>handle</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>flip</span> <span class='hs-varid'>catch</span>
<a name="line-333"></a>
<a name="line-334"></a><a name="handleJust"></a><span class='hs-comment'>-- | A version of 'catchJust' with the arguments swapped around (see</span>
<a name="line-335"></a><span class='hs-comment'>-- 'handle').</span>
<a name="line-336"></a><span class='hs-definition'>handleJust</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</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-337"></a><span class='hs-definition'>handleJust</span> <span class='hs-varid'>p</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>flip</span> <span class='hs-layout'>(</span><span class='hs-varid'>catchJust</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span>
<a name="line-338"></a>
<a name="line-339"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-340"></a><span class='hs-comment'>-- 'mapException'</span>
<a name="line-341"></a>
<a name="line-342"></a><span class='hs-comment'>-- | This function maps one exception into another as proposed in the</span>
<a name="line-343"></a><span class='hs-comment'>-- paper \"A semantics for imprecise exceptions\".</span>
<a name="line-344"></a>
<a name="line-345"></a><span class='hs-comment'>-- Notice that the usage of 'unsafePerformIO' is safe here.</span>
<a name="line-346"></a>
<a name="line-347"></a><a name="mapException"></a><span class='hs-definition'>mapException</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Exception</span> <span class='hs-varid'>e1</span><span class='hs-layout'>,</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-varid'>e1</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>e2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-348"></a><span class='hs-definition'>mapException</span> <span class='hs-varid'>f</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePerformIO</span> <span class='hs-layout'>(</span><span class='hs-varid'>catch</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>evaluate</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span>
<a name="line-349"></a> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>x</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>throw</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-350"></a>
<a name="line-351"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-352"></a><span class='hs-comment'>-- 'try' and variations.</span>
<a name="line-353"></a>
<a name="line-354"></a><span class='hs-comment'>-- | Similar to 'catch', but returns an 'Either' result which is</span>
<a name="line-355"></a><span class='hs-comment'>-- @('Right' a)@ if no exception was raised, or @('Left' e)@ if an</span>
<a name="line-356"></a><span class='hs-comment'>-- exception was raised and its value is @e@.</span>
<a name="line-357"></a><span class='hs-comment'>--</span>
<a name="line-358"></a><span class='hs-comment'>-- > try a = catch (Right `liftM` a) (return . Left)</span>
<a name="line-359"></a><span class='hs-comment'>--</span>
<a name="line-360"></a><span class='hs-comment'>-- Note: as with 'catch', it is only polite to use this variant if you intend</span>
<a name="line-361"></a><span class='hs-comment'>-- to re-throw the exception after performing whatever cleanup is needed.</span>
<a name="line-362"></a><span class='hs-comment'>-- Otherwise, 'tryJust' is generally considered to be better.</span>
<a name="line-363"></a><span class='hs-comment'>--</span>
<a name="line-364"></a><span class='hs-comment'>-- Also note that "System.IO.Error" also exports a function called</span>
<a name="line-365"></a><span class='hs-comment'>-- 'System.IO.Error.try' with a similar type to 'Control.Exception.try',</span>
<a name="line-366"></a><span class='hs-comment'>-- except that it catches only the IO and user families of exceptions</span>
<a name="line-367"></a><span class='hs-comment'>-- (as required by the Haskell 98 @IO@ module).</span>
<a name="line-368"></a>
<a name="line-369"></a><a name="try"></a><span class='hs-definition'>try</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>IO</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'>Either</span> <span class='hs-varid'>e</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-370"></a><span class='hs-definition'>try</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>catch</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-varop'>>>=</span> <span class='hs-keyglyph'>\</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-371"></a>
<a name="line-372"></a><a name="tryJust"></a><span class='hs-comment'>-- | A variant of 'try' that takes an exception predicate to select</span>
<a name="line-373"></a><span class='hs-comment'>-- which exceptions are caught (c.f. 'catchJust'). If the exception</span>
<a name="line-374"></a><span class='hs-comment'>-- does not match the predicate, it is re-thrown.</span>
<a name="line-375"></a><span class='hs-definition'>tryJust</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</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'>Either</span> <span class='hs-varid'>b</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-376"></a><span class='hs-definition'>tryJust</span> <span class='hs-varid'>p</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-377"></a> <span class='hs-varid'>r</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>try</span> <span class='hs-varid'>a</span>
<a name="line-378"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>r</span> <span class='hs-keyword'>of</span>
<a name="line-379"></a> <span class='hs-conid'>Right</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span>
<a name="line-380"></a> <span class='hs-conid'>Left</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>p</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-381"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>throw</span> <span class='hs-varid'>e</span>
<a name="line-382"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-383"></a>
<a name="line-384"></a>
<a name="line-385"></a><span class='hs-comment'>-------------</span>
<a name="line-386"></a>
<a name="line-387"></a>
<a name="line-388"></a>
<a name="line-389"></a><a name="Handler"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Handler</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>forall</span> <span class='hs-varid'>e</span> <span class='hs-varop'>.</span> <span class='hs-conid'>Exception</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Handler</span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-390"></a>
<a name="line-391"></a><a name="catches"></a><span class='hs-definition'>catches</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Handler</span> <span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-392"></a><span class='hs-definition'>catches</span> <span class='hs-varid'>io</span> <span class='hs-varid'>handlers</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>io</span> <span class='hs-varop'>`catch`</span> <span class='hs-varid'>catchesHandler</span> <span class='hs-varid'>handlers</span>
<a name="line-393"></a>
<a name="line-394"></a><a name="catchesHandler"></a><span class='hs-definition'>catchesHandler</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Handler</span> <span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>SomeException</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-395"></a><span class='hs-definition'>catchesHandler</span> <span class='hs-varid'>handlers</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldr</span> <span class='hs-varid'>tryHandler</span> <span class='hs-layout'>(</span><span class='hs-varid'>throw</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-varid'>handlers</span>
<a name="line-396"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>tryHandler</span> <span class='hs-layout'>(</span><span class='hs-conid'>Handler</span> <span class='hs-varid'>handler</span><span class='hs-layout'>)</span> <span class='hs-varid'>res</span>
<a name="line-397"></a> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>fromException</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-398"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>e'</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>handler</span> <span class='hs-varid'>e'</span>
<a name="line-399"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>res</span>
<a name="line-400"></a>
<a name="line-401"></a>
<a name="line-402"></a><span class='hs-comment'>-- -----------------------------------------------------------------------------</span>
<a name="line-403"></a><span class='hs-comment'>-- Asynchronous exceptions</span>
<a name="line-404"></a>
<a name="line-405"></a><span class='hs-comment'>{- $async
<a name="line-406"></a>
<a name="line-407"></a> #AsynchronousExceptions# Asynchronous exceptions are so-called because they arise due to
<a name="line-408"></a>external influences, and can be raised at any point during execution.
<a name="line-409"></a>'StackOverflow' and 'HeapOverflow' are two examples of
<a name="line-410"></a>system-generated asynchronous exceptions.
<a name="line-411"></a>
<a name="line-412"></a>The primary source of asynchronous exceptions, however, is
<a name="line-413"></a>'throwTo':
<a name="line-414"></a>
<a name="line-415"></a>> throwTo :: ThreadId -> Exception -> IO ()
<a name="line-416"></a>
<a name="line-417"></a>'throwTo' (also 'throwDynTo' and 'Control.Concurrent.killThread') allows one
<a name="line-418"></a>running thread to raise an arbitrary exception in another thread. The
<a name="line-419"></a>exception is therefore asynchronous with respect to the target thread,
<a name="line-420"></a>which could be doing anything at the time it receives the exception.
<a name="line-421"></a>Great care should be taken with asynchronous exceptions; it is all too
<a name="line-422"></a>easy to introduce race conditions by the over zealous use of
<a name="line-423"></a>'throwTo'.
<a name="line-424"></a>-}</span>
<a name="line-425"></a>
<a name="line-426"></a><span class='hs-comment'>{- $block_handler
<a name="line-427"></a>There\'s an implied 'block' around every exception handler in a call
<a name="line-428"></a>to one of the 'catch' family of functions. This is because that is
<a name="line-429"></a>what you want most of the time - it eliminates a common race condition
<a name="line-430"></a>in starting an exception handler, because there may be no exception
<a name="line-431"></a>handler on the stack to handle another exception if one arrives
<a name="line-432"></a>immediately. If asynchronous exceptions are blocked on entering the
<a name="line-433"></a>handler, though, we have time to install a new exception handler
<a name="line-434"></a>before being interrupted. If this weren\'t the default, one would have
<a name="line-435"></a>to write something like
<a name="line-436"></a>
<a name="line-437"></a>> block (
<a name="line-438"></a>> catch (unblock (...))
<a name="line-439"></a>> (\e -> handler)
<a name="line-440"></a>> )
<a name="line-441"></a>
<a name="line-442"></a>If you need to unblock asynchronous exceptions again in the exception
<a name="line-443"></a>handler, just use 'unblock' as normal.
<a name="line-444"></a>
<a name="line-445"></a>Note that 'try' and friends /do not/ have a similar default, because
<a name="line-446"></a>there is no exception handler in this case. If you want to use 'try'
<a name="line-447"></a>in an asynchronous-exception-safe way, you will need to use
<a name="line-448"></a>'block'.
<a name="line-449"></a>-}</span>
<a name="line-450"></a>
<a name="line-451"></a><span class='hs-comment'>{- $interruptible
<a name="line-452"></a>
<a name="line-453"></a>Some operations are /interruptible/, which means that they can receive
<a name="line-454"></a>asynchronous exceptions even in the scope of a 'block'. Any function
<a name="line-455"></a>which may itself block is defined as interruptible; this includes
<a name="line-456"></a>'Control.Concurrent.MVar.takeMVar'
<a name="line-457"></a>(but not 'Control.Concurrent.MVar.tryTakeMVar'),
<a name="line-458"></a>and most operations which perform
<a name="line-459"></a>some I\/O with the outside world. The reason for having
<a name="line-460"></a>interruptible operations is so that we can write things like
<a name="line-461"></a>
<a name="line-462"></a>> block (
<a name="line-463"></a>> a <- takeMVar m
<a name="line-464"></a>> catch (unblock (...))
<a name="line-465"></a>> (\e -> ...)
<a name="line-466"></a>> )
<a name="line-467"></a>
<a name="line-468"></a>if the 'Control.Concurrent.MVar.takeMVar' was not interruptible,
<a name="line-469"></a>then this particular
<a name="line-470"></a>combination could lead to deadlock, because the thread itself would be
<a name="line-471"></a>blocked in a state where it can\'t receive any asynchronous exceptions.
<a name="line-472"></a>With 'Control.Concurrent.MVar.takeMVar' interruptible, however, we can be
<a name="line-473"></a>safe in the knowledge that the thread can receive exceptions right up
<a name="line-474"></a>until the point when the 'Control.Concurrent.MVar.takeMVar' succeeds.
<a name="line-475"></a>Similar arguments apply for other interruptible operations like
<a name="line-476"></a>'System.IO.openFile'.
<a name="line-477"></a>-}</span>
<a name="line-478"></a>
<a name="line-479"></a>
<a name="line-480"></a><span class='hs-comment'>----------------------------------------------------------------------</span>
<a name="line-481"></a><span class='hs-comment'>-- Exception instance for the legacy Exception type</span>
<a name="line-482"></a>
<a name="line-483"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span>
<a name="line-484"></a>
<a name="line-485"></a><span class='hs-comment'>----------------------------------------------------------------------</span>
<a name="line-486"></a><span class='hs-comment'>-- The new Exception types. These need to map to/from E.Exception so</span>
<a name="line-487"></a><span class='hs-comment'>-- that uses of legacy catch/throw functions work.</span>
<a name="line-488"></a>
<a name="line-489"></a><span class='hs-comment'>----</span>
<a name="line-490"></a>
<a name="line-491"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ArithException</span> <span class='hs-keyword'>where</span>
<a name="line-492"></a> <span class='hs-varid'>toException</span> <span class='hs-varid'>ae</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ArithException</span> <span class='hs-varid'>ae</span><span class='hs-layout'>)</span>
<a name="line-493"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-494"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ArithException</span> <span class='hs-varid'>ae</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-495"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>ae</span>
<a name="line-496"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-497"></a><span class='hs-comment'>----</span>
<a name="line-498"></a>
<a name="line-499"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ArrayException</span> <span class='hs-keyword'>where</span>
<a name="line-500"></a> <span class='hs-varid'>toException</span> <span class='hs-varid'>ae</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ArrayException</span> <span class='hs-varid'>ae</span><span class='hs-layout'>)</span>
<a name="line-501"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-502"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ArrayException</span> <span class='hs-varid'>ae</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-503"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>ae</span>
<a name="line-504"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-505"></a>
<a name="line-506"></a><span class='hs-comment'>----</span>
<a name="line-507"></a>
<a name="line-508"></a><a name="AssertionFailed"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>AssertionFailed</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>AssertionFailed</span> <span class='hs-conid'>String</span>
<a name="line-509"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-510"></a>
<a name="line-511"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>AssertionFailed</span> <span class='hs-keyword'>where</span>
<a name="line-512"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>AssertionFailed</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>AssertionFailed</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-513"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-514"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>AssertionFailed</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-515"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>AssertionFailed</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-516"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-517"></a>
<a name="line-518"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>AssertionFailed</span> <span class='hs-keyword'>where</span>
<a name="line-519"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>AssertionFailed</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showString</span> <span class='hs-varid'>err</span>
<a name="line-520"></a>
<a name="line-521"></a><span class='hs-comment'>-----</span>
<a name="line-522"></a>
<a name="line-523"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>AsyncException</span> <span class='hs-keyword'>where</span>
<a name="line-524"></a> <span class='hs-varid'>toException</span> <span class='hs-varid'>ae</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>AsyncException</span> <span class='hs-varid'>ae</span><span class='hs-layout'>)</span>
<a name="line-525"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-526"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>AsyncException</span> <span class='hs-varid'>ae</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-527"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>ae</span>
<a name="line-528"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-529"></a>
<a name="line-530"></a><span class='hs-comment'>----</span>
<a name="line-531"></a>
<a name="line-532"></a><a name="BlockedOnDeadMVar"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>BlockedOnDeadMVar</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>BlockedOnDeadMVar</span>
<a name="line-533"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-534"></a>
<a name="line-535"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>BlockedOnDeadMVar</span> <span class='hs-keyword'>where</span>
<a name="line-536"></a> <span class='hs-varid'>toException</span> <span class='hs-conid'>BlockedOnDeadMVar</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedOnDeadMVar</span><span class='hs-layout'>)</span>
<a name="line-537"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-538"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedOnDeadMVar</span> <span class='hs-keyglyph'>-></span>
<a name="line-539"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>BlockedOnDeadMVar</span>
<a name="line-540"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-541"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>BlockedOnDeadMVar</span> <span class='hs-keyword'>where</span>
<a name="line-542"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>BlockedOnDeadMVar</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedOnDeadMVar</span>
<a name="line-543"></a>
<a name="line-544"></a><span class='hs-comment'>----</span>
<a name="line-545"></a>
<a name="line-546"></a><a name="BlockedIndefinitely"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>BlockedIndefinitely</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>BlockedIndefinitely</span>
<a name="line-547"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-548"></a>
<a name="line-549"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>BlockedIndefinitely</span> <span class='hs-keyword'>where</span>
<a name="line-550"></a> <span class='hs-varid'>toException</span> <span class='hs-conid'>BlockedIndefinitely</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedIndefinitely</span>
<a name="line-551"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-552"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedIndefinitely</span> <span class='hs-keyglyph'>-></span>
<a name="line-553"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>BlockedIndefinitely</span>
<a name="line-554"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-555"></a>
<a name="line-556"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>BlockedIndefinitely</span> <span class='hs-keyword'>where</span>
<a name="line-557"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>BlockedIndefinitely</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedIndefinitely</span>
<a name="line-558"></a>
<a name="line-559"></a><span class='hs-comment'>----</span>
<a name="line-560"></a>
<a name="line-561"></a><a name="NestedAtomically"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>NestedAtomically</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>NestedAtomically</span>
<a name="line-562"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-563"></a>
<a name="line-564"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>NestedAtomically</span> <span class='hs-keyword'>where</span>
<a name="line-565"></a> <span class='hs-varid'>toException</span> <span class='hs-conid'>NestedAtomically</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>NestedAtomically</span>
<a name="line-566"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-567"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>NestedAtomically</span> <span class='hs-keyglyph'>-></span>
<a name="line-568"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>NestedAtomically</span>
<a name="line-569"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-570"></a>
<a name="line-571"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>NestedAtomically</span> <span class='hs-keyword'>where</span>
<a name="line-572"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>NestedAtomically</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>NestedAtomically</span>
<a name="line-573"></a>
<a name="line-574"></a><span class='hs-comment'>----</span>
<a name="line-575"></a>
<a name="line-576"></a><a name="Deadlock"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Deadlock</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Deadlock</span>
<a name="line-577"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-578"></a>
<a name="line-579"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>Deadlock</span> <span class='hs-keyword'>where</span>
<a name="line-580"></a> <span class='hs-varid'>toException</span> <span class='hs-conid'>Deadlock</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>Deadlock</span>
<a name="line-581"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-582"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>Deadlock</span> <span class='hs-keyglyph'>-></span>
<a name="line-583"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>Deadlock</span>
<a name="line-584"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-585"></a>
<a name="line-586"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>Deadlock</span> <span class='hs-keyword'>where</span>
<a name="line-587"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>Deadlock</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>Deadlock</span>
<a name="line-588"></a>
<a name="line-589"></a><span class='hs-comment'>-----</span>
<a name="line-590"></a>
<a name="line-591"></a><a name="ErrorCall"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>ErrorCall</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ErrorCall</span> <span class='hs-conid'>String</span>
<a name="line-592"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-593"></a>
<a name="line-594"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>ErrorCall</span> <span class='hs-keyword'>where</span>
<a name="line-595"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-596"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-597"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-598"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-599"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-600"></a>
<a name="line-601"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>ErrorCall</span> <span class='hs-keyword'>where</span>
<a name="line-602"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showString</span> <span class='hs-varid'>err</span>
<a name="line-603"></a>
<a name="line-604"></a><span class='hs-comment'>-----</span>
<a name="line-605"></a>
<a name="line-606"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Typeable</span> <span class='hs-conid'>ExitCode</span> <span class='hs-keyword'>where</span>
<a name="line-607"></a> <span class='hs-varid'>typeOf</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mkTyConApp</span> <span class='hs-layout'>(</span><span class='hs-varid'>mkTyCon</span> <span class='hs-str'>"ExitCode"</span><span class='hs-layout'>)</span> <span class='hs-conid'>[]</span>
<a name="line-608"></a>
<a name="line-609"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>ExitCode</span> <span class='hs-keyword'>where</span>
<a name="line-610"></a> <span class='hs-varid'>toException</span> <span class='hs-varid'>ee</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ExitException</span> <span class='hs-varid'>ee</span><span class='hs-layout'>)</span>
<a name="line-611"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-612"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>ExitException</span> <span class='hs-varid'>ee</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-613"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>ee</span>
<a name="line-614"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-615"></a><span class='hs-comment'>-----</span>
<a name="line-616"></a>
<a name="line-617"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>IOException</span> <span class='hs-keyword'>where</span>
<a name="line-618"></a> <span class='hs-varid'>toException</span> <span class='hs-varid'>ioe</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>IOException</span> <span class='hs-varid'>ioe</span><span class='hs-layout'>)</span>
<a name="line-619"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-620"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>IOException</span> <span class='hs-varid'>ioe</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-621"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>ioe</span>
<a name="line-622"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-623"></a>
<a name="line-624"></a><span class='hs-comment'>----</span>
<a name="line-625"></a>
<a name="line-626"></a><a name="NoMethodError"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>NoMethodError</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>NoMethodError</span> <span class='hs-conid'>String</span>
<a name="line-627"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-628"></a>
<a name="line-629"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>NoMethodError</span> <span class='hs-keyword'>where</span>
<a name="line-630"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-631"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-632"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-633"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-634"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-635"></a>
<a name="line-636"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>NoMethodError</span> <span class='hs-keyword'>where</span>
<a name="line-637"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showString</span> <span class='hs-varid'>str</span>
<a name="line-638"></a>
<a name="line-639"></a><span class='hs-comment'>----</span>
<a name="line-640"></a>
<a name="line-641"></a><a name="NonTermination"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>NonTermination</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>NonTermination</span>
<a name="line-642"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-643"></a>
<a name="line-644"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>NonTermination</span> <span class='hs-keyword'>where</span>
<a name="line-645"></a> <span class='hs-varid'>toException</span> <span class='hs-conid'>NonTermination</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>NonTermination</span>
<a name="line-646"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-647"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>NonTermination</span> <span class='hs-keyglyph'>-></span>
<a name="line-648"></a> <span class='hs-conid'>Just</span> <span class='hs-conid'>NonTermination</span>
<a name="line-649"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-650"></a>
<a name="line-651"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>NonTermination</span> <span class='hs-keyword'>where</span>
<a name="line-652"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>NonTermination</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>n</span> <span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>NonTermination</span>
<a name="line-653"></a>
<a name="line-654"></a><span class='hs-comment'>----</span>
<a name="line-655"></a>
<a name="line-656"></a><a name="PatternMatchFail"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>PatternMatchFail</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PatternMatchFail</span> <span class='hs-conid'>String</span>
<a name="line-657"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-658"></a>
<a name="line-659"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>PatternMatchFail</span> <span class='hs-keyword'>where</span>
<a name="line-660"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-661"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-662"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-663"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-664"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-665"></a>
<a name="line-666"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>PatternMatchFail</span> <span class='hs-keyword'>where</span>
<a name="line-667"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showString</span> <span class='hs-varid'>str</span>
<a name="line-668"></a>
<a name="line-669"></a>
<a name="line-670"></a><span class='hs-comment'>----</span>
<a name="line-671"></a>
<a name="line-672"></a><a name="RecConError"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>RecConError</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RecConError</span> <span class='hs-conid'>String</span>
<a name="line-673"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-674"></a>
<a name="line-675"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>RecConError</span> <span class='hs-keyword'>where</span>
<a name="line-676"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecConError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>RecConError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-677"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-678"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>RecConError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-679"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecConError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-680"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-681"></a>
<a name="line-682"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>RecConError</span> <span class='hs-keyword'>where</span>
<a name="line-683"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecConError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showString</span> <span class='hs-varid'>str</span>
<a name="line-684"></a>
<a name="line-685"></a>
<a name="line-686"></a>
<a name="line-687"></a><span class='hs-comment'>----</span>
<a name="line-688"></a>
<a name="line-689"></a><a name="RecSelError"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>RecSelError</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RecSelError</span> <span class='hs-conid'>String</span>
<a name="line-690"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-691"></a>
<a name="line-692"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>RecSelError</span> <span class='hs-keyword'>where</span>
<a name="line-693"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecSelError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>RecSelError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-694"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-695"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>RecSelError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-696"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecSelError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-697"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-698"></a>
<a name="line-699"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>RecSelError</span> <span class='hs-keyword'>where</span>
<a name="line-700"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecSelError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showString</span> <span class='hs-varid'>str</span>
<a name="line-701"></a>
<a name="line-702"></a><span class='hs-comment'>----</span>
<a name="line-703"></a>
<a name="line-704"></a><a name="RecUpdError"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>RecUpdError</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RecUpdError</span> <span class='hs-conid'>String</span>
<a name="line-705"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-706"></a>
<a name="line-707"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>RecUpdError</span> <span class='hs-keyword'>where</span>
<a name="line-708"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-709"></a> <span class='hs-varid'>fromException</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>cast</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-710"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-711"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span>
<a name="line-712"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-713"></a>
<a name="line-714"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>RecUpdError</span> <span class='hs-keyword'>where</span>
<a name="line-715"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>str</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showString</span> <span class='hs-varid'>str</span>
<a name="line-716"></a>
<a name="line-717"></a>
<a name="line-718"></a><span class='hs-cpp'>#endif</span>
<a name="line-719"></a>
</pre></body>
</html>
