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<pre><a name="line-1"></a><span class='hs-comment'>{-# OPTIONS_GHC -XNoImplicitPrelude #-}</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-cpp'>#include "Typeable.h"</span>
<a name="line-4"></a>
<a name="line-5"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-6"></a><span class='hs-comment'>-- |</span>
<a name="line-7"></a><span class='hs-comment'>-- Module : Control.OldException</span>
<a name="line-8"></a><span class='hs-comment'>-- Copyright : (c) The University of Glasgow 2001</span>
<a name="line-9"></a><span class='hs-comment'>-- License : BSD-style (see the file libraries/base/LICENSE)</span>
<a name="line-10"></a><span class='hs-comment'>-- </span>
<a name="line-11"></a><span class='hs-comment'>-- Maintainer : libraries@haskell.org</span>
<a name="line-12"></a><span class='hs-comment'>-- Stability : experimental</span>
<a name="line-13"></a><span class='hs-comment'>-- Portability : non-portable (extended exceptions)</span>
<a name="line-14"></a><span class='hs-comment'>--</span>
<a name="line-15"></a><span class='hs-comment'>-- This module provides support for raising and catching both built-in</span>
<a name="line-16"></a><span class='hs-comment'>-- and user-defined exceptions.</span>
<a name="line-17"></a><span class='hs-comment'>--</span>
<a name="line-18"></a><span class='hs-comment'>-- In addition to exceptions thrown by 'IO' operations, exceptions may</span>
<a name="line-19"></a><span class='hs-comment'>-- be thrown by pure code (imprecise exceptions) or by external events</span>
<a name="line-20"></a><span class='hs-comment'>-- (asynchronous exceptions), but may only be caught in the 'IO' monad.</span>
<a name="line-21"></a><span class='hs-comment'>-- For more details, see:</span>
<a name="line-22"></a><span class='hs-comment'>--</span>
<a name="line-23"></a><span class='hs-comment'>-- * /A semantics for imprecise exceptions/, by Simon Peyton Jones,</span>
<a name="line-24"></a><span class='hs-comment'>-- Alastair Reid, Tony Hoare, Simon Marlow, Fergus Henderson,</span>
<a name="line-25"></a><span class='hs-comment'>-- in /PLDI'99/.</span>
<a name="line-26"></a><span class='hs-comment'>--</span>
<a name="line-27"></a><span class='hs-comment'>-- * /Asynchronous exceptions in Haskell/, by Simon Marlow, Simon Peyton</span>
<a name="line-28"></a><span class='hs-comment'>-- Jones, Andy Moran and John Reppy, in /PLDI'01/.</span>
<a name="line-29"></a><span class='hs-comment'>--</span>
<a name="line-30"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-31"></a>
<a name="line-32"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>OldException</span> <span class='hs-comment'>{-# DEPRECATED "Future versions of base will not support the old exceptions style. Please switch to extensible exceptions." #-}</span> <span class='hs-layout'>(</span>
<a name="line-33"></a>
<a name="line-34"></a> <span class='hs-comment'>-- * The Exception type</span>
<a name="line-35"></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> <span class='hs-comment'>-- instance Eq, Ord, Show, Typeable</span>
<a name="line-36"></a> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>IOException</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- instance Eq, Ord, Show, Typeable</span>
<a name="line-37"></a> <span class='hs-conid'>New</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> <span class='hs-comment'>-- instance Eq, Ord, Show, Typeable</span>
<a name="line-38"></a> <span class='hs-conid'>New</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> <span class='hs-comment'>-- instance Eq, Ord, Show, Typeable</span>
<a name="line-39"></a> <span class='hs-conid'>New</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> <span class='hs-comment'>-- instance Eq, Ord, Show, Typeable</span>
<a name="line-40"></a>
<a name="line-41"></a> <span class='hs-comment'>-- * Throwing exceptions</span>
<a name="line-42"></a> <span class='hs-varid'>throwIO</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Exception -> IO a</span>
<a name="line-43"></a> <span class='hs-varid'>throw</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Exception -> a</span>
<a name="line-44"></a> <span class='hs-varid'>ioError</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: IOError -> IO a</span>
<a name="line-45"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span>
<a name="line-46"></a> <span class='hs-comment'>-- XXX Need to restrict the type of this:</span>
<a name="line-47"></a> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-varid'>throwTo</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: ThreadId -> Exception -> a</span>
<a name="line-48"></a><span class='hs-cpp'>#endif</span>
<a name="line-49"></a>
<a name="line-50"></a> <span class='hs-comment'>-- * Catching Exceptions</span>
<a name="line-51"></a>
<a name="line-52"></a> <span class='hs-comment'>-- |There are several functions for catching and examining</span>
<a name="line-53"></a> <span class='hs-comment'>-- exceptions; all of them may only be used from within the</span>
<a name="line-54"></a> <span class='hs-comment'>-- 'IO' monad.</span>
<a name="line-55"></a>
<a name="line-56"></a> <span class='hs-comment'>-- ** The @catch@ functions</span>
<a name="line-57"></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-58"></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-59"></a>
<a name="line-60"></a> <span class='hs-comment'>-- ** The @handle@ functions</span>
<a name="line-61"></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-62"></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-63"></a>
<a name="line-64"></a> <span class='hs-comment'>-- ** The @try@ functions</span>
<a name="line-65"></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-66"></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-67"></a>
<a name="line-68"></a> <span class='hs-comment'>-- ** The @evaluate@ function</span>
<a name="line-69"></a> <span class='hs-varid'>evaluate</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: a -> IO a</span>
<a name="line-70"></a>
<a name="line-71"></a> <span class='hs-comment'>-- ** The @mapException@ function</span>
<a name="line-72"></a> <span class='hs-varid'>mapException</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: (Exception -> Exception) -> a -> a</span>
<a name="line-73"></a>
<a name="line-74"></a> <span class='hs-comment'>-- ** Exception predicates</span>
<a name="line-75"></a>
<a name="line-76"></a> <span class='hs-comment'>-- $preds</span>
<a name="line-77"></a>
<a name="line-78"></a> <span class='hs-varid'>ioErrors</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Exception -> Maybe IOError</span>
<a name="line-79"></a> <span class='hs-varid'>arithExceptions</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Exception -> Maybe ArithException</span>
<a name="line-80"></a> <span class='hs-varid'>errorCalls</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Exception -> Maybe String</span>
<a name="line-81"></a> <span class='hs-varid'>dynExceptions</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Exception -> Maybe Dynamic</span>
<a name="line-82"></a> <span class='hs-varid'>assertions</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Exception -> Maybe String</span>
<a name="line-83"></a> <span class='hs-varid'>asyncExceptions</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Exception -> Maybe AsyncException</span>
<a name="line-84"></a> <span class='hs-varid'>userErrors</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Exception -> Maybe String</span>
<a name="line-85"></a>
<a name="line-86"></a> <span class='hs-comment'>-- * Dynamic exceptions</span>
<a name="line-87"></a>
<a name="line-88"></a> <span class='hs-comment'>-- $dynamic</span>
<a name="line-89"></a> <span class='hs-varid'>throwDyn</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Typeable ex => ex -> b</span>
<a name="line-90"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span>
<a name="line-91"></a> <span class='hs-varid'>throwDynTo</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Typeable ex => ThreadId -> ex -> b</span>
<a name="line-92"></a><span class='hs-cpp'>#endif</span>
<a name="line-93"></a> <span class='hs-varid'>catchDyn</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Typeable ex => IO a -> (ex -> IO a) -> IO a</span>
<a name="line-94"></a>
<a name="line-95"></a> <span class='hs-comment'>-- * Asynchronous Exceptions</span>
<a name="line-96"></a>
<a name="line-97"></a> <span class='hs-comment'>-- $async</span>
<a name="line-98"></a>
<a name="line-99"></a> <span class='hs-comment'>-- ** Asynchronous exception control</span>
<a name="line-100"></a>
<a name="line-101"></a> <span class='hs-comment'>-- |The following two functions allow a thread to control delivery of</span>
<a name="line-102"></a> <span class='hs-comment'>-- asynchronous exceptions during a critical region.</span>
<a name="line-103"></a>
<a name="line-104"></a> <span class='hs-varid'>block</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: IO a -> IO a</span>
<a name="line-105"></a> <span class='hs-varid'>unblock</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: IO a -> IO a</span>
<a name="line-106"></a>
<a name="line-107"></a> <span class='hs-comment'>-- *** Applying @block@ to an exception handler</span>
<a name="line-108"></a>
<a name="line-109"></a> <span class='hs-comment'>-- $block_handler</span>
<a name="line-110"></a>
<a name="line-111"></a> <span class='hs-comment'>-- *** Interruptible operations</span>
<a name="line-112"></a>
<a name="line-113"></a> <span class='hs-comment'>-- $interruptible</span>
<a name="line-114"></a>
<a name="line-115"></a> <span class='hs-comment'>-- * Assertions</span>
<a name="line-116"></a>
<a name="line-117"></a> <span class='hs-varid'>assert</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: Bool -> a -> a</span>
<a name="line-118"></a>
<a name="line-119"></a> <span class='hs-comment'>-- * Utilities</span>
<a name="line-120"></a>
<a name="line-121"></a> <span class='hs-varid'>bracket</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: IO a -> (a -> IO b) -> (a -> IO c) -> IO ()</span>
<a name="line-122"></a> <span class='hs-varid'>bracket_</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: IO a -> IO b -> IO c -> IO ()</span>
<a name="line-123"></a> <span class='hs-varid'>bracketOnError</span><span class='hs-layout'>,</span>
<a name="line-124"></a>
<a name="line-125"></a> <span class='hs-varid'>finally</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: IO a -> IO b -> IO a</span>
<a name="line-126"></a>
<a name="line-127"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span>
<a name="line-128"></a> <span class='hs-varid'>setUncaughtExceptionHandler</span><span class='hs-layout'>,</span> <span class='hs-comment'>-- :: (Exception -> IO ()) -> IO ()</span>
<a name="line-129"></a> <span class='hs-varid'>getUncaughtExceptionHandler</span> <span class='hs-comment'>-- :: IO (Exception -> IO ())</span>
<a name="line-130"></a><span class='hs-cpp'>#endif</span>
<a name="line-131"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-132"></a>
<a name="line-133"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span>
<a name="line-134"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Base</span>
<a name="line-135"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Show</span>
<a name="line-136"></a><span class='hs-comment'>-- import GHC.IO ( IO )</span>
<a name="line-137"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span><span class='hs-varop'>.</span><span class='hs-conid'>Handle</span><span class='hs-varop'>.</span><span class='hs-conid'>FD</span> <span class='hs-layout'>(</span> <span class='hs-varid'>stdout</span> <span class='hs-layout'>)</span>
<a name="line-138"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>New</span>
<a name="line-139"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>New</span>
<a name="line-140"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Conc</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span><span class='hs-varid'>setUncaughtExceptionHandler</span><span class='hs-layout'>,</span>
<a name="line-141"></a> <span class='hs-varid'>getUncaughtExceptionHandler</span><span class='hs-layout'>)</span>
<a name="line-142"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>IORef</span> <span class='hs-layout'>(</span> <span class='hs-conid'>IORef</span><span class='hs-layout'>,</span> <span class='hs-varid'>newIORef</span><span class='hs-layout'>,</span> <span class='hs-varid'>readIORef</span><span class='hs-layout'>,</span> <span class='hs-varid'>writeIORef</span> <span class='hs-layout'>)</span>
<a name="line-143"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Foreign</span><span class='hs-varop'>.</span><span class='hs-conid'>C</span><span class='hs-varop'>.</span><span class='hs-conid'>String</span> <span class='hs-layout'>(</span> <span class='hs-conid'>CString</span><span class='hs-layout'>,</span> <span class='hs-varid'>withCString</span> <span class='hs-layout'>)</span>
<a name="line-144"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span><span class='hs-varop'>.</span><span class='hs-conid'>Handle</span> <span class='hs-layout'>(</span> <span class='hs-varid'>hFlush</span> <span class='hs-layout'>)</span>
<a name="line-145"></a><span class='hs-cpp'>#endif</span>
<a name="line-146"></a>
<a name="line-147"></a><span class='hs-cpp'>#ifdef __HUGS__</span>
<a name="line-148"></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-149"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Hugs</span><span class='hs-varop'>.</span><span class='hs-conid'>Prelude</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>New</span> <span class='hs-layout'>(</span><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-150"></a><span class='hs-cpp'>#endif</span>
<a name="line-151"></a>
<a name="line-152"></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'>New</span>
<a name="line-153"></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-layout'>(</span> <span class='hs-varid'>toException</span><span class='hs-layout'>,</span> <span class='hs-varid'>fromException</span><span class='hs-layout'>,</span> <span class='hs-varid'>throw</span><span class='hs-layout'>,</span> <span class='hs-varid'>block</span><span class='hs-layout'>,</span> <span class='hs-varid'>unblock</span><span class='hs-layout'>,</span> <span class='hs-varid'>mask</span><span class='hs-layout'>,</span> <span class='hs-varid'>evaluate</span><span class='hs-layout'>,</span> <span class='hs-varid'>throwIO</span> <span class='hs-layout'>)</span>
<a name="line-154"></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'>Error</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span> <span class='hs-varid'>catch</span><span class='hs-layout'>,</span> <span class='hs-varid'>try</span> <span class='hs-layout'>)</span>
<a name="line-155"></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-156"></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-157"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Either</span>
<a name="line-158"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Maybe</span>
<a name="line-159"></a>
<a name="line-160"></a><span class='hs-cpp'>#ifdef __NHC__</span>
<a name="line-161"></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'>Error</span> <span class='hs-layout'>(</span><span class='hs-varid'>catch</span><span class='hs-layout'>,</span> <span class='hs-varid'>ioError</span><span class='hs-layout'>)</span>
<a name="line-162"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-varid'>bracket</span><span class='hs-layout'>)</span>
<a name="line-163"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>DIOError</span> <span class='hs-comment'>-- defn of IOError type</span>
<a name="line-164"></a>
<a name="line-165"></a><a name="Exception"></a><span class='hs-comment'>-- minimum needed for nhc98 to pretend it has Exceptions</span>
<a name="line-166"></a><a name="Exception"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>IOError</span>
<a name="line-167"></a><a name="IOException"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>IOException</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>IOError</span>
<a name="line-168"></a><a name="ArithException"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>ArithException</span>
<a name="line-169"></a><a name="ArrayException"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>ArrayException</span>
<a name="line-170"></a><a name="AsyncException"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>AsyncException</span>
<a name="line-171"></a>
<a name="line-172"></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-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-173"></a><span class='hs-definition'>throwIO</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ioError</span>
<a name="line-174"></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-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-175"></a><span class='hs-definition'>throw</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePerformIO</span> <span class='hs-varop'>.</span> <span class='hs-varid'>throwIO</span>
<a name="line-176"></a>
<a name="line-177"></a><a name="evaluate"></a><span class='hs-definition'>evaluate</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-178"></a><span class='hs-definition'>evaluate</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span> <span class='hs-varop'>`seq`</span> <span class='hs-varid'>return</span> <span class='hs-varid'>x</span>
<a name="line-179"></a>
<a name="line-180"></a><a name="ioErrors"></a><span class='hs-definition'>ioErrors</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>IOError</span>
<a name="line-181"></a><span class='hs-definition'>ioErrors</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>e</span>
<a name="line-182"></a><a name="arithExceptions"></a><span class='hs-definition'>arithExceptions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>ArithException</span>
<a name="line-183"></a><span class='hs-definition'>arithExceptions</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>const</span> <span class='hs-conid'>Nothing</span>
<a name="line-184"></a><a name="errorCalls"></a><span class='hs-definition'>errorCalls</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>String</span>
<a name="line-185"></a><span class='hs-definition'>errorCalls</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>const</span> <span class='hs-conid'>Nothing</span>
<a name="line-186"></a><a name="dynExceptions"></a><span class='hs-definition'>dynExceptions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>Dynamic</span>
<a name="line-187"></a><span class='hs-definition'>dynExceptions</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>const</span> <span class='hs-conid'>Nothing</span>
<a name="line-188"></a><a name="assertions"></a><span class='hs-definition'>assertions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>String</span>
<a name="line-189"></a><span class='hs-definition'>assertions</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>const</span> <span class='hs-conid'>Nothing</span>
<a name="line-190"></a><a name="asyncExceptions"></a><span class='hs-definition'>asyncExceptions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>AsyncException</span>
<a name="line-191"></a><span class='hs-definition'>asyncExceptions</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>const</span> <span class='hs-conid'>Nothing</span>
<a name="line-192"></a><a name="userErrors"></a><span class='hs-definition'>userErrors</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>String</span>
<a name="line-193"></a><span class='hs-definition'>userErrors</span> <span class='hs-layout'>(</span><span class='hs-conid'>UserError</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>s</span>
<a name="line-194"></a><span class='hs-definition'>userErrors</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-195"></a>
<a name="line-196"></a><a name="block"></a><span class='hs-definition'>block</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-197"></a><span class='hs-definition'>block</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>id</span>
<a name="line-198"></a><a name="unblock"></a><span class='hs-definition'>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-199"></a><span class='hs-definition'>unblock</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>id</span>
<a name="line-200"></a>
<a name="line-201"></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-202"></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-203"></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'>UserError</span> <span class='hs-str'>""</span> <span class='hs-str'>"Assertion failed"</span><span class='hs-layout'>)</span>
<a name="line-204"></a><span class='hs-cpp'>#endif</span>
<a name="line-205"></a>
<a name="line-206"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-207"></a><span class='hs-comment'>-- Catching exceptions</span>
<a name="line-208"></a>
<a name="line-209"></a><span class='hs-comment'>-- |This is the simplest of the exception-catching functions. It</span>
<a name="line-210"></a><span class='hs-comment'>-- takes a single argument, runs it, and if an exception is raised</span>
<a name="line-211"></a><span class='hs-comment'>-- the \"handler\" is executed, with the value of the exception passed as an</span>
<a name="line-212"></a><span class='hs-comment'>-- argument. Otherwise, the result is returned as normal. For example:</span>
<a name="line-213"></a><span class='hs-comment'>--</span>
<a name="line-214"></a><span class='hs-comment'>-- > catch (openFile f ReadMode) </span>
<a name="line-215"></a><span class='hs-comment'>-- > (\e -> hPutStr stderr ("Couldn't open "++f++": " ++ show e))</span>
<a name="line-216"></a><span class='hs-comment'>--</span>
<a name="line-217"></a><span class='hs-comment'>-- For catching exceptions in pure (non-'IO') expressions, see the</span>
<a name="line-218"></a><span class='hs-comment'>-- function 'evaluate'.</span>
<a name="line-219"></a><span class='hs-comment'>--</span>
<a name="line-220"></a><span class='hs-comment'>-- Note that due to Haskell\'s unspecified evaluation order, an</span>
<a name="line-221"></a><span class='hs-comment'>-- expression may return one of several possible exceptions: consider</span>
<a name="line-222"></a><span class='hs-comment'>-- the expression @error \"urk\" + 1 \`div\` 0@. Does</span>
<a name="line-223"></a><span class='hs-comment'>-- 'catch' execute the handler passing</span>
<a name="line-224"></a><span class='hs-comment'>-- @ErrorCall \"urk\"@, or @ArithError DivideByZero@?</span>
<a name="line-225"></a><span class='hs-comment'>--</span>
<a name="line-226"></a><span class='hs-comment'>-- The answer is \"either\": 'catch' makes a</span>
<a name="line-227"></a><span class='hs-comment'>-- non-deterministic choice about which exception to catch. If you</span>
<a name="line-228"></a><span class='hs-comment'>-- call it again, you might get a different exception back. This is</span>
<a name="line-229"></a><span class='hs-comment'>-- ok, because 'catch' is an 'IO' computation.</span>
<a name="line-230"></a><span class='hs-comment'>--</span>
<a name="line-231"></a><span class='hs-comment'>-- Note that 'catch' catches all types of exceptions, and is generally</span>
<a name="line-232"></a><span class='hs-comment'>-- used for \"cleaning up\" before passing on the exception using</span>
<a name="line-233"></a><span class='hs-comment'>-- 'throwIO'. It is not good practice to discard the exception and</span>
<a name="line-234"></a><span class='hs-comment'>-- continue, without first checking the type of the exception (it</span>
<a name="line-235"></a><span class='hs-comment'>-- might be a 'ThreadKilled', for example). In this case it is usually better</span>
<a name="line-236"></a><span class='hs-comment'>-- to use 'catchJust' and select the kinds of exceptions to catch.</span>
<a name="line-237"></a><span class='hs-comment'>--</span>
<a name="line-238"></a><span class='hs-comment'>-- Also note that the "Prelude" also exports a function called</span>
<a name="line-239"></a><span class='hs-comment'>-- 'Prelude.catch' with a similar type to 'Control.OldException.catch',</span>
<a name="line-240"></a><span class='hs-comment'>-- except that the "Prelude" version only catches the IO and user</span>
<a name="line-241"></a><span class='hs-comment'>-- families of exceptions (as required by Haskell 98). </span>
<a name="line-242"></a><span class='hs-comment'>--</span>
<a name="line-243"></a><span class='hs-comment'>-- We recommend either hiding the "Prelude" version of 'Prelude.catch'</span>
<a name="line-244"></a><span class='hs-comment'>-- when importing "Control.OldException": </span>
<a name="line-245"></a><span class='hs-comment'>--</span>
<a name="line-246"></a><span class='hs-comment'>-- > import Prelude hiding (catch)</span>
<a name="line-247"></a><span class='hs-comment'>--</span>
<a name="line-248"></a><span class='hs-comment'>-- or importing "Control.OldException" qualified, to avoid name-clashes:</span>
<a name="line-249"></a><span class='hs-comment'>--</span>
<a name="line-250"></a><span class='hs-comment'>-- > import qualified Control.OldException as C</span>
<a name="line-251"></a><span class='hs-comment'>--</span>
<a name="line-252"></a><span class='hs-comment'>-- and then using @C.catch@</span>
<a name="line-253"></a><span class='hs-comment'>--</span>
<a name="line-254"></a>
<a name="line-255"></a><a name="catch"></a><span class='hs-definition'>catch</span> <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-256"></a> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Exception</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-257"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-258"></a><span class='hs-comment'>-- note: bundling the exceptions is done in the New.Exception</span>
<a name="line-259"></a><span class='hs-comment'>-- instance of Exception; see below.</span>
<a name="line-260"></a><span class='hs-definition'>catch</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-varid'>catch</span>
<a name="line-261"></a>
<a name="line-262"></a><a name="catchJust"></a><span class='hs-comment'>-- | The function 'catchJust' is like 'catch', but it takes an extra</span>
<a name="line-263"></a><span class='hs-comment'>-- argument which is an /exception predicate/, a function which</span>
<a name="line-264"></a><span class='hs-comment'>-- selects which type of exceptions we\'re interested in. There are</span>
<a name="line-265"></a><span class='hs-comment'>-- some predefined exception predicates for useful subsets of</span>
<a name="line-266"></a><span class='hs-comment'>-- exceptions: 'ioErrors', 'arithExceptions', and so on. For example,</span>
<a name="line-267"></a><span class='hs-comment'>-- to catch just calls to the 'error' function, we could use</span>
<a name="line-268"></a><span class='hs-comment'>--</span>
<a name="line-269"></a><span class='hs-comment'>-- > result <- catchJust errorCalls thing_to_try handler</span>
<a name="line-270"></a><span class='hs-comment'>--</span>
<a name="line-271"></a><span class='hs-comment'>-- Any other exceptions which are not matched by the predicate</span>
<a name="line-272"></a><span class='hs-comment'>-- are re-raised, and may be caught by an enclosing</span>
<a name="line-273"></a><span class='hs-comment'>-- 'catch' or 'catchJust'.</span>
<a name="line-274"></a><span class='hs-definition'>catchJust</span>
<a name="line-275"></a> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Exception</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-276"></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-277"></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-278"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-279"></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-280"></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-281"></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-282"></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-283"></a>
<a name="line-284"></a><a name="handle"></a><span class='hs-comment'>-- | A version of 'catch' with the arguments swapped around; useful in</span>
<a name="line-285"></a><span class='hs-comment'>-- situations where the code for the handler is shorter. For example:</span>
<a name="line-286"></a><span class='hs-comment'>--</span>
<a name="line-287"></a><span class='hs-comment'>-- > do handle (\e -> exitWith (ExitFailure 1)) $</span>
<a name="line-288"></a><span class='hs-comment'>-- > ...</span>
<a name="line-289"></a><span class='hs-definition'>handle</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Exception</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-290"></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-291"></a>
<a name="line-292"></a><a name="handleJust"></a><span class='hs-comment'>-- | A version of 'catchJust' with the arguments swapped around (see</span>
<a name="line-293"></a><span class='hs-comment'>-- 'handle').</span>
<a name="line-294"></a><span class='hs-definition'>handleJust</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Exception</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-295"></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-296"></a>
<a name="line-297"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-298"></a><span class='hs-comment'>-- 'mapException'</span>
<a name="line-299"></a>
<a name="line-300"></a><span class='hs-comment'>-- | This function maps one exception into another as proposed in the</span>
<a name="line-301"></a><span class='hs-comment'>-- paper \"A semantics for imprecise exceptions\".</span>
<a name="line-302"></a>
<a name="line-303"></a><span class='hs-comment'>-- Notice that the usage of 'unsafePerformIO' is safe here.</span>
<a name="line-304"></a>
<a name="line-305"></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-keyglyph'>-></span> <span class='hs-conid'>Exception</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-306"></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-varid'>evaluate</span> <span class='hs-varid'>v</span><span class='hs-layout'>)</span>
<a name="line-307"></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-308"></a>
<a name="line-309"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-310"></a><span class='hs-comment'>-- 'try' and variations.</span>
<a name="line-311"></a>
<a name="line-312"></a><span class='hs-comment'>-- | Similar to 'catch', but returns an 'Either' result which is</span>
<a name="line-313"></a><span class='hs-comment'>-- @('Right' a)@ if no exception was raised, or @('Left' e)@ if an</span>
<a name="line-314"></a><span class='hs-comment'>-- exception was raised and its value is @e@.</span>
<a name="line-315"></a><span class='hs-comment'>--</span>
<a name="line-316"></a><span class='hs-comment'>-- > try a = catch (Right `liftM` a) (return . Left)</span>
<a name="line-317"></a><span class='hs-comment'>--</span>
<a name="line-318"></a><span class='hs-comment'>-- Note: as with 'catch', it is only polite to use this variant if you intend</span>
<a name="line-319"></a><span class='hs-comment'>-- to re-throw the exception after performing whatever cleanup is needed.</span>
<a name="line-320"></a><span class='hs-comment'>-- Otherwise, 'tryJust' is generally considered to be better.</span>
<a name="line-321"></a><span class='hs-comment'>--</span>
<a name="line-322"></a><span class='hs-comment'>-- Also note that "System.IO.Error" also exports a function called</span>
<a name="line-323"></a><span class='hs-comment'>-- 'System.IO.Error.try' with a similar type to 'Control.OldException.try',</span>
<a name="line-324"></a><span class='hs-comment'>-- except that it catches only the IO and user families of exceptions</span>
<a name="line-325"></a><span class='hs-comment'>-- (as required by the Haskell 98 @IO@ module).</span>
<a name="line-326"></a>
<a name="line-327"></a><a name="try"></a><span class='hs-definition'>try</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-conid'>Exception</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-328"></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-329"></a>
<a name="line-330"></a><a name="tryJust"></a><span class='hs-comment'>-- | A variant of 'try' that takes an exception predicate to select</span>
<a name="line-331"></a><span class='hs-comment'>-- which exceptions are caught (c.f. 'catchJust'). If the exception</span>
<a name="line-332"></a><span class='hs-comment'>-- does not match the predicate, it is re-thrown.</span>
<a name="line-333"></a><span class='hs-definition'>tryJust</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Exception</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-334"></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-335"></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-336"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>r</span> <span class='hs-keyword'>of</span>
<a name="line-337"></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-338"></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-339"></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-340"></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-341"></a>
<a name="line-342"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-343"></a><span class='hs-comment'>-- Dynamic exceptions</span>
<a name="line-344"></a>
<a name="line-345"></a><span class='hs-comment'>-- $dynamic</span>
<a name="line-346"></a><span class='hs-comment'>-- #DynamicExceptions# Because the 'Exception' datatype is not extensible, there is an</span>
<a name="line-347"></a><span class='hs-comment'>-- interface for throwing and catching exceptions of type 'Dynamic'</span>
<a name="line-348"></a><span class='hs-comment'>-- (see "Data.Dynamic") which allows exception values of any type in</span>
<a name="line-349"></a><span class='hs-comment'>-- the 'Typeable' class to be thrown and caught.</span>
<a name="line-350"></a>
<a name="line-351"></a><a name="throwDyn"></a><span class='hs-comment'>-- | Raise any value as an exception, provided it is in the</span>
<a name="line-352"></a><span class='hs-comment'>-- 'Typeable' class.</span>
<a name="line-353"></a><span class='hs-definition'>throwDyn</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Typeable</span> <span class='hs-varid'>exception</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span>
<a name="line-354"></a><span class='hs-cpp'>#ifdef __NHC__</span>
<a name="line-355"></a><span class='hs-definition'>throwDyn</span> <span class='hs-varid'>exception</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>throw</span> <span class='hs-layout'>(</span><span class='hs-conid'>UserError</span> <span class='hs-str'>""</span> <span class='hs-str'>"dynamic exception"</span><span class='hs-layout'>)</span>
<a name="line-356"></a><span class='hs-cpp'>#else</span>
<a name="line-357"></a><span class='hs-definition'>throwDyn</span> <span class='hs-varid'>exception</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>throw</span> <span class='hs-layout'>(</span><span class='hs-conid'>DynException</span> <span class='hs-layout'>(</span><span class='hs-varid'>toDyn</span> <span class='hs-varid'>exception</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-358"></a><span class='hs-cpp'>#endif</span>
<a name="line-359"></a>
<a name="line-360"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span>
<a name="line-361"></a><a name="throwDynTo"></a><span class='hs-comment'>-- | A variant of 'throwDyn' that throws the dynamic exception to an</span>
<a name="line-362"></a><span class='hs-comment'>-- arbitrary thread (GHC only: c.f. 'throwTo').</span>
<a name="line-363"></a><span class='hs-definition'>throwDynTo</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Typeable</span> <span class='hs-varid'>exception</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ThreadId</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span>
<a name="line-364"></a><span class='hs-definition'>throwDynTo</span> <span class='hs-varid'>t</span> <span class='hs-varid'>exception</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-varid'>throwTo</span> <span class='hs-varid'>t</span> <span class='hs-layout'>(</span><span class='hs-conid'>DynException</span> <span class='hs-layout'>(</span><span class='hs-varid'>toDyn</span> <span class='hs-varid'>exception</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-365"></a><span class='hs-cpp'>#endif /* __GLASGOW_HASKELL__ */</span>
<a name="line-366"></a>
<a name="line-367"></a><a name="catchDyn"></a><span class='hs-comment'>-- | Catch dynamic exceptions of the required type. All other</span>
<a name="line-368"></a><span class='hs-comment'>-- exceptions are re-thrown, including dynamic exceptions of the wrong</span>
<a name="line-369"></a><span class='hs-comment'>-- type.</span>
<a name="line-370"></a><span class='hs-comment'>--</span>
<a name="line-371"></a><span class='hs-comment'>-- When using dynamic exceptions it is advisable to define a new</span>
<a name="line-372"></a><span class='hs-comment'>-- datatype to use for your exception type, to avoid possible clashes</span>
<a name="line-373"></a><span class='hs-comment'>-- with dynamic exceptions used in other libraries.</span>
<a name="line-374"></a><span class='hs-comment'>--</span>
<a name="line-375"></a><span class='hs-definition'>catchDyn</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Typeable</span> <span class='hs-varid'>exception</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-layout'>(</span><span class='hs-varid'>exception</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>
<a name="line-376"></a><span class='hs-cpp'>#ifdef __NHC__</span>
<a name="line-377"></a><span class='hs-definition'>catchDyn</span> <span class='hs-varid'>m</span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>m</span> <span class='hs-comment'>-- can't catch dyn exceptions in nhc98</span>
<a name="line-378"></a><span class='hs-cpp'>#else</span>
<a name="line-379"></a><span class='hs-definition'>catchDyn</span> <span class='hs-varid'>m</span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-varid'>catch</span> <span class='hs-varid'>m</span> <span class='hs-varid'>handler</span>
<a name="line-380"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>handler</span> <span class='hs-varid'>ex</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>ex</span> <span class='hs-keyword'>of</span>
<a name="line-381"></a> <span class='hs-layout'>(</span><span class='hs-conid'>DynException</span> <span class='hs-varid'>dyn</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-382"></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-383"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>k</span> <span class='hs-varid'>exception</span>
<a name="line-384"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>throw</span> <span class='hs-varid'>ex</span>
<a name="line-385"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>throw</span> <span class='hs-varid'>ex</span>
<a name="line-386"></a><span class='hs-cpp'>#endif</span>
<a name="line-387"></a>
<a name="line-388"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-389"></a><span class='hs-comment'>-- Exception Predicates</span>
<a name="line-390"></a>
<a name="line-391"></a><span class='hs-comment'>-- $preds</span>
<a name="line-392"></a><span class='hs-comment'>-- These pre-defined predicates may be used as the first argument to</span>
<a name="line-393"></a><span class='hs-comment'>-- 'catchJust', 'tryJust', or 'handleJust' to select certain common</span>
<a name="line-394"></a><span class='hs-comment'>-- classes of exceptions.</span>
<a name="line-395"></a><span class='hs-cpp'>#ifndef __NHC__</span>
<a name="line-396"></a><span class='hs-definition'>ioErrors</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>IOError</span>
<a name="line-397"></a><span class='hs-definition'>arithExceptions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>ArithException</span>
<a name="line-398"></a><span class='hs-definition'>errorCalls</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>String</span>
<a name="line-399"></a><span class='hs-definition'>assertions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>String</span>
<a name="line-400"></a><span class='hs-definition'>dynExceptions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>Dynamic</span>
<a name="line-401"></a><span class='hs-definition'>asyncExceptions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>AsyncException</span>
<a name="line-402"></a><span class='hs-definition'>userErrors</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-conid'>String</span>
<a name="line-403"></a>
<a name="line-404"></a><span class='hs-definition'>ioErrors</span> <span class='hs-layout'>(</span><span class='hs-conid'>IOException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>e</span>
<a name="line-405"></a><span class='hs-definition'>ioErrors</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-406"></a>
<a name="line-407"></a><span class='hs-definition'>arithExceptions</span> <span class='hs-layout'>(</span><span class='hs-conid'>ArithException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>e</span>
<a name="line-408"></a><span class='hs-definition'>arithExceptions</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-409"></a>
<a name="line-410"></a><span class='hs-definition'>errorCalls</span> <span class='hs-layout'>(</span><span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>e</span>
<a name="line-411"></a><span class='hs-definition'>errorCalls</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-412"></a>
<a name="line-413"></a><span class='hs-definition'>assertions</span> <span class='hs-layout'>(</span><span class='hs-conid'>AssertionFailed</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>e</span>
<a name="line-414"></a><span class='hs-definition'>assertions</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-415"></a>
<a name="line-416"></a><span class='hs-definition'>dynExceptions</span> <span class='hs-layout'>(</span><span class='hs-conid'>DynException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>e</span>
<a name="line-417"></a><span class='hs-definition'>dynExceptions</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-418"></a>
<a name="line-419"></a><span class='hs-definition'>asyncExceptions</span> <span class='hs-layout'>(</span><span class='hs-conid'>AsyncException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>e</span>
<a name="line-420"></a><span class='hs-definition'>asyncExceptions</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-421"></a>
<a name="line-422"></a><span class='hs-definition'>userErrors</span> <span class='hs-layout'>(</span><span class='hs-conid'>IOException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>isUserError</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>ioeGetErrorString</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span>
<a name="line-423"></a><span class='hs-definition'>userErrors</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-424"></a><span class='hs-cpp'>#endif</span>
<a name="line-425"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-426"></a><span class='hs-comment'>-- Some Useful Functions</span>
<a name="line-427"></a>
<a name="line-428"></a><span class='hs-comment'>-- | When you want to acquire a resource, do some work with it, and</span>
<a name="line-429"></a><span class='hs-comment'>-- then release the resource, it is a good idea to use 'bracket',</span>
<a name="line-430"></a><span class='hs-comment'>-- because 'bracket' will install the necessary exception handler to</span>
<a name="line-431"></a><span class='hs-comment'>-- release the resource in the event that an exception is raised</span>
<a name="line-432"></a><span class='hs-comment'>-- during the computation. If an exception is raised, then 'bracket' will </span>
<a name="line-433"></a><span class='hs-comment'>-- re-raise the exception (after performing the release).</span>
<a name="line-434"></a><span class='hs-comment'>--</span>
<a name="line-435"></a><span class='hs-comment'>-- A common example is opening a file:</span>
<a name="line-436"></a><span class='hs-comment'>--</span>
<a name="line-437"></a><span class='hs-comment'>-- > bracket</span>
<a name="line-438"></a><span class='hs-comment'>-- > (openFile "filename" ReadMode)</span>
<a name="line-439"></a><span class='hs-comment'>-- > (hClose)</span>
<a name="line-440"></a><span class='hs-comment'>-- > (\handle -> do { ... })</span>
<a name="line-441"></a><span class='hs-comment'>--</span>
<a name="line-442"></a><span class='hs-comment'>-- The arguments to 'bracket' are in this order so that we can partially apply </span>
<a name="line-443"></a><span class='hs-comment'>-- it, e.g.:</span>
<a name="line-444"></a><span class='hs-comment'>--</span>
<a name="line-445"></a><span class='hs-comment'>-- > withFile name mode = bracket (openFile name mode) hClose</span>
<a name="line-446"></a><span class='hs-comment'>--</span>
<a name="line-447"></a><span class='hs-cpp'>#ifndef __NHC__</span>
<a name="line-448"></a><a name="bracket"></a><span class='hs-definition'>bracket</span>
<a name="line-449"></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-450"></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-451"></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-452"></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-453"></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-454"></a> <span class='hs-varid'>mask</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>restore</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-455"></a> <span class='hs-varid'>a</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>before</span>
<a name="line-456"></a> <span class='hs-varid'>r</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>catch</span>
<a name="line-457"></a> <span class='hs-layout'>(</span><span class='hs-varid'>restore</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-layout'>)</span>
<a name="line-458"></a> <span class='hs-layout'>(</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-layout'>{</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>after</span> <span class='hs-varid'>a</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-layout'>)</span>
<a name="line-459"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>after</span> <span class='hs-varid'>a</span>
<a name="line-460"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>r</span>
<a name="line-461"></a><span class='hs-cpp'>#endif</span>
<a name="line-462"></a>
<a name="line-463"></a><a name="finally"></a><span class='hs-comment'>-- | A specialised variant of 'bracket' with just a computation to run</span>
<a name="line-464"></a><span class='hs-comment'>-- afterward.</span>
<a name="line-465"></a><span class='hs-comment'>-- </span>
<a name="line-466"></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-467"></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-468"></a> <span class='hs-comment'>-- was raised)</span>
<a name="line-469"></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-470"></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-471"></a> <span class='hs-varid'>mask</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>restore</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-472"></a> <span class='hs-varid'>r</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>catch</span>
<a name="line-473"></a> <span class='hs-layout'>(</span><span class='hs-varid'>restore</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-474"></a> <span class='hs-layout'>(</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-layout'>{</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>sequel</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-layout'>)</span>
<a name="line-475"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>sequel</span>
<a name="line-476"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>r</span>
<a name="line-477"></a>
<a name="line-478"></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-479"></a><span class='hs-comment'>-- is not required.</span>
<a name="line-480"></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-481"></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-482"></a>
<a name="line-483"></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-484"></a><span class='hs-comment'>-- exception raised by the in-between computation.</span>
<a name="line-485"></a><span class='hs-definition'>bracketOnError</span>
<a name="line-486"></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-487"></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-488"></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-489"></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-490"></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-491"></a> <span class='hs-varid'>mask</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>restore</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-492"></a> <span class='hs-varid'>a</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>before</span>
<a name="line-493"></a> <span class='hs-varid'>catch</span>
<a name="line-494"></a> <span class='hs-layout'>(</span><span class='hs-varid'>restore</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-layout'>)</span>
<a name="line-495"></a> <span class='hs-layout'>(</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-layout'>{</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>after</span> <span class='hs-varid'>a</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-layout'>)</span>
<a name="line-496"></a>
<a name="line-497"></a><span class='hs-comment'>-- -----------------------------------------------------------------------------</span>
<a name="line-498"></a><span class='hs-comment'>-- Asynchronous exceptions</span>
<a name="line-499"></a>
<a name="line-500"></a><span class='hs-comment'>{- $async
<a name="line-501"></a>
<a name="line-502"></a> #AsynchronousExceptions# Asynchronous exceptions are so-called because they arise due to
<a name="line-503"></a>external influences, and can be raised at any point during execution.
<a name="line-504"></a>'StackOverflow' and 'HeapOverflow' are two examples of
<a name="line-505"></a>system-generated asynchronous exceptions.
<a name="line-506"></a>
<a name="line-507"></a>The primary source of asynchronous exceptions, however, is
<a name="line-508"></a>'throwTo':
<a name="line-509"></a>
<a name="line-510"></a>> throwTo :: ThreadId -> Exception -> IO ()
<a name="line-511"></a>
<a name="line-512"></a>'throwTo' (also 'throwDynTo' and 'Control.Concurrent.killThread') allows one
<a name="line-513"></a>running thread to raise an arbitrary exception in another thread. The
<a name="line-514"></a>exception is therefore asynchronous with respect to the target thread,
<a name="line-515"></a>which could be doing anything at the time it receives the exception.
<a name="line-516"></a>Great care should be taken with asynchronous exceptions; it is all too
<a name="line-517"></a>easy to introduce race conditions by the over zealous use of
<a name="line-518"></a>'throwTo'.
<a name="line-519"></a>-}</span>
<a name="line-520"></a>
<a name="line-521"></a><span class='hs-comment'>{- $block_handler
<a name="line-522"></a>There\'s an implied 'mask_' around every exception handler in a call
<a name="line-523"></a>to one of the 'catch' family of functions. This is because that is
<a name="line-524"></a>what you want most of the time - it eliminates a common race condition
<a name="line-525"></a>in starting an exception handler, because there may be no exception
<a name="line-526"></a>handler on the stack to handle another exception if one arrives
<a name="line-527"></a>immediately. If asynchronous exceptions are blocked on entering the
<a name="line-528"></a>handler, though, we have time to install a new exception handler
<a name="line-529"></a>before being interrupted. If this weren\'t the default, one would have
<a name="line-530"></a>to write something like
<a name="line-531"></a>
<a name="line-532"></a>> mask $ \restore ->
<a name="line-533"></a>> catch (restore (...))
<a name="line-534"></a>> (\e -> handler)
<a name="line-535"></a>
<a name="line-536"></a>If you need to unblock asynchronous exceptions again in the exception
<a name="line-537"></a>handler, just use 'unblock' as normal.
<a name="line-538"></a>
<a name="line-539"></a>Note that 'try' and friends /do not/ have a similar default, because
<a name="line-540"></a>there is no exception handler in this case. If you want to use 'try'
<a name="line-541"></a>in an asynchronous-exception-safe way, you will need to use
<a name="line-542"></a>'mask'.
<a name="line-543"></a>-}</span>
<a name="line-544"></a>
<a name="line-545"></a><span class='hs-comment'>{- $interruptible
<a name="line-546"></a>
<a name="line-547"></a>Some operations are /interruptible/, which means that they can receive
<a name="line-548"></a>asynchronous exceptions even in the scope of a 'mask'. Any function
<a name="line-549"></a>which may itself block is defined as interruptible; this includes
<a name="line-550"></a>'Control.Concurrent.MVar.takeMVar'
<a name="line-551"></a>(but not 'Control.Concurrent.MVar.tryTakeMVar'),
<a name="line-552"></a>and most operations which perform
<a name="line-553"></a>some I\/O with the outside world. The reason for having
<a name="line-554"></a>interruptible operations is so that we can write things like
<a name="line-555"></a>
<a name="line-556"></a>> mask $ \restore -> do
<a name="line-557"></a>> a <- takeMVar m
<a name="line-558"></a>> catch (restore (...))
<a name="line-559"></a>> (\e -> ...)
<a name="line-560"></a>
<a name="line-561"></a>if the 'Control.Concurrent.MVar.takeMVar' was not interruptible,
<a name="line-562"></a>then this particular
<a name="line-563"></a>combination could lead to deadlock, because the thread itself would be
<a name="line-564"></a>blocked in a state where it can\'t receive any asynchronous exceptions.
<a name="line-565"></a>With 'Control.Concurrent.MVar.takeMVar' interruptible, however, we can be
<a name="line-566"></a>safe in the knowledge that the thread can receive exceptions right up
<a name="line-567"></a>until the point when the 'Control.Concurrent.MVar.takeMVar' succeeds.
<a name="line-568"></a>Similar arguments apply for other interruptible operations like
<a name="line-569"></a>'System.IO.openFile'.
<a name="line-570"></a>-}</span>
<a name="line-571"></a>
<a name="line-572"></a><span class='hs-cpp'>#if !(__GLASGOW_HASKELL__ || __NHC__)</span>
<a name="line-573"></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-574"></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-575"></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-576"></a><span class='hs-cpp'>#endif</span>
<a name="line-577"></a>
<a name="line-578"></a>
<a name="line-579"></a><span class='hs-cpp'>#ifdef __GLASGOW_HASKELL__</span>
<a name="line-580"></a><a name="uncaughtExceptionHandler"></a><span class='hs-comment'>{-# NOINLINE uncaughtExceptionHandler #-}</span>
<a name="line-581"></a><span class='hs-definition'>uncaughtExceptionHandler</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IORef</span> <span class='hs-layout'>(</span><span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span>
<a name="line-582"></a><span class='hs-definition'>uncaughtExceptionHandler</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePerformIO</span> <span class='hs-layout'>(</span><span class='hs-varid'>newIORef</span> <span class='hs-varid'>defaultHandler</span><span class='hs-layout'>)</span>
<a name="line-583"></a> <span class='hs-keyword'>where</span>
<a name="line-584"></a> <span class='hs-varid'>defaultHandler</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span>
<a name="line-585"></a> <span class='hs-varid'>defaultHandler</span> <span class='hs-varid'>ex</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-586"></a> <span class='hs-layout'>(</span><span class='hs-varid'>hFlush</span> <span class='hs-varid'>stdout</span><span class='hs-layout'>)</span> <span class='hs-varop'>`</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-varid'>catchAny</span><span class='hs-varop'>`</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span>
<a name="line-587"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>msg</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>ex</span> <span class='hs-keyword'>of</span>
<a name="line-588"></a> <span class='hs-conid'>Deadlock</span> <span class='hs-keyglyph'>-></span> <span class='hs-str'>"no threads to run: infinite loop or deadlock?"</span>
<a name="line-589"></a> <span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>s</span>
<a name="line-590"></a> <span class='hs-varid'>other</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>showsPrec</span> <span class='hs-num'>0</span> <span class='hs-varid'>other</span> <span class='hs-str'>""</span>
<a name="line-591"></a> <span class='hs-varid'>withCString</span> <span class='hs-str'>"%s"</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>cfmt</span> <span class='hs-keyglyph'>-></span>
<a name="line-592"></a> <span class='hs-varid'>withCString</span> <span class='hs-varid'>msg</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>cmsg</span> <span class='hs-keyglyph'>-></span>
<a name="line-593"></a> <span class='hs-varid'>errorBelch</span> <span class='hs-varid'>cfmt</span> <span class='hs-varid'>cmsg</span>
<a name="line-594"></a>
<a name="line-595"></a><span class='hs-comment'>-- don't use errorBelch() directly, because we cannot call varargs functions</span>
<a name="line-596"></a><span class='hs-comment'>-- using the FFI.</span>
<a name="line-597"></a><span class='hs-keyword'>foreign</span> <span class='hs-keyword'>import</span> <span class='hs-keyword'>ccall</span> <span class='hs-keyword'>unsafe</span> <span class='hs-str'>"HsBase.h errorBelch2"</span>
<a name="line-598"></a> <span class='hs-varid'>errorBelch</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>CString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>CString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span>
<a name="line-599"></a>
<a name="line-600"></a><a name="setUncaughtExceptionHandler"></a><span class='hs-definition'>setUncaughtExceptionHandler</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span>
<a name="line-601"></a><span class='hs-definition'>setUncaughtExceptionHandler</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>writeIORef</span> <span class='hs-varid'>uncaughtExceptionHandler</span>
<a name="line-602"></a>
<a name="line-603"></a><a name="getUncaughtExceptionHandler"></a><span class='hs-definition'>getUncaughtExceptionHandler</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>Exception</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span>
<a name="line-604"></a><span class='hs-definition'>getUncaughtExceptionHandler</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>readIORef</span> <span class='hs-varid'>uncaughtExceptionHandler</span>
<a name="line-605"></a><span class='hs-cpp'>#endif</span>
<a name="line-606"></a>
<a name="line-607"></a><span class='hs-comment'>-- ------------------------------------------------------------------------</span>
<a name="line-608"></a><span class='hs-comment'>-- Exception datatype and operations</span>
<a name="line-609"></a>
<a name="line-610"></a><a name="Exception"></a><span class='hs-comment'>-- |The type of exceptions. Every kind of system-generated exception</span>
<a name="line-611"></a><a name="Exception"></a><span class='hs-comment'>-- has a constructor in the 'Exception' type, and values of other</span>
<a name="line-612"></a><a name="Exception"></a><span class='hs-comment'>-- types may be injected into 'Exception' by coercing them to</span>
<a name="line-613"></a><a name="Exception"></a><span class='hs-comment'>-- 'Data.Dynamic.Dynamic' (see the section on Dynamic Exceptions:</span>
<a name="line-614"></a><a name="Exception"></a><span class='hs-comment'>-- "Control.OldException\#DynamicExceptions").</span>
<a name="line-615"></a><a name="Exception"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Exception</span>
<a name="line-616"></a> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ArithException</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>ArithException</span>
<a name="line-617"></a> <span class='hs-comment'>-- ^Exceptions raised by arithmetic</span>
<a name="line-618"></a> <span class='hs-comment'>-- operations. (NOTE: GHC currently does not throw</span>
<a name="line-619"></a> <span class='hs-comment'>-- 'ArithException's except for 'DivideByZero').</span>
<a name="line-620"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>ArrayException</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>ArrayException</span>
<a name="line-621"></a> <span class='hs-comment'>-- ^Exceptions raised by array-related</span>
<a name="line-622"></a> <span class='hs-comment'>-- operations. (NOTE: GHC currently does not throw</span>
<a name="line-623"></a> <span class='hs-comment'>-- 'ArrayException's).</span>
<a name="line-624"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>AssertionFailed</span> <span class='hs-conid'>String</span>
<a name="line-625"></a> <span class='hs-comment'>-- ^This exception is thrown by the</span>
<a name="line-626"></a> <span class='hs-comment'>-- 'assert' operation when the condition</span>
<a name="line-627"></a> <span class='hs-comment'>-- fails. The 'String' argument contains the</span>
<a name="line-628"></a> <span class='hs-comment'>-- location of the assertion in the source program.</span>
<a name="line-629"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>AsyncException</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>AsyncException</span>
<a name="line-630"></a> <span class='hs-comment'>-- ^Asynchronous exceptions (see section on Asynchronous Exceptions: "Control.OldException\#AsynchronousExceptions").</span>
<a name="line-631"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>BlockedOnDeadMVar</span>
<a name="line-632"></a> <span class='hs-comment'>-- ^The current thread was executing a call to</span>
<a name="line-633"></a> <span class='hs-comment'>-- 'Control.Concurrent.MVar.takeMVar' that could never return,</span>
<a name="line-634"></a> <span class='hs-comment'>-- because there are no other references to this 'MVar'.</span>
<a name="line-635"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>BlockedIndefinitely</span>
<a name="line-636"></a> <span class='hs-comment'>-- ^The current thread was waiting to retry an atomic memory transaction</span>
<a name="line-637"></a> <span class='hs-comment'>-- that could never become possible to complete because there are no other</span>
<a name="line-638"></a> <span class='hs-comment'>-- threads referring to any of the TVars involved.</span>
<a name="line-639"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>NestedAtomically</span>
<a name="line-640"></a> <span class='hs-comment'>-- ^The runtime detected an attempt to nest one STM transaction</span>
<a name="line-641"></a> <span class='hs-comment'>-- inside another one, presumably due to the use of </span>
<a name="line-642"></a> <span class='hs-comment'>-- 'unsafePeformIO' with 'atomically'.</span>
<a name="line-643"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Deadlock</span>
<a name="line-644"></a> <span class='hs-comment'>-- ^There are no runnable threads, so the program is</span>
<a name="line-645"></a> <span class='hs-comment'>-- deadlocked. The 'Deadlock' exception is</span>
<a name="line-646"></a> <span class='hs-comment'>-- raised in the main thread only (see also: "Control.Concurrent").</span>
<a name="line-647"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>DynException</span> <span class='hs-conid'>Dynamic</span>
<a name="line-648"></a> <span class='hs-comment'>-- ^Dynamically typed exceptions (see section on Dynamic Exceptions: "Control.OldException\#DynamicExceptions").</span>
<a name="line-649"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>ErrorCall</span> <span class='hs-conid'>String</span>
<a name="line-650"></a> <span class='hs-comment'>-- ^The 'ErrorCall' exception is thrown by 'error'. The 'String'</span>
<a name="line-651"></a> <span class='hs-comment'>-- argument of 'ErrorCall' is the string passed to 'error' when it was</span>
<a name="line-652"></a> <span class='hs-comment'>-- called.</span>
<a name="line-653"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>ExitException</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>ExitCode</span>
<a name="line-654"></a> <span class='hs-comment'>-- ^The 'ExitException' exception is thrown by 'System.Exit.exitWith' (and</span>
<a name="line-655"></a> <span class='hs-comment'>-- 'System.Exit.exitFailure'). The 'ExitCode' argument is the value passed </span>
<a name="line-656"></a> <span class='hs-comment'>-- to 'System.Exit.exitWith'. An unhandled 'ExitException' exception in the</span>
<a name="line-657"></a> <span class='hs-comment'>-- main thread will cause the program to be terminated with the given </span>
<a name="line-658"></a> <span class='hs-comment'>-- exit code.</span>
<a name="line-659"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>IOException</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>IOException</span>
<a name="line-660"></a> <span class='hs-comment'>-- ^These are the standard IO exceptions generated by</span>
<a name="line-661"></a> <span class='hs-comment'>-- Haskell\'s @IO@ operations. See also "System.IO.Error".</span>
<a name="line-662"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>NoMethodError</span> <span class='hs-conid'>String</span>
<a name="line-663"></a> <span class='hs-comment'>-- ^An attempt was made to invoke a class method which has</span>
<a name="line-664"></a> <span class='hs-comment'>-- no definition in this instance, and there was no default</span>
<a name="line-665"></a> <span class='hs-comment'>-- definition given in the class declaration. GHC issues a</span>
<a name="line-666"></a> <span class='hs-comment'>-- warning when you compile an instance which has missing</span>
<a name="line-667"></a> <span class='hs-comment'>-- methods.</span>
<a name="line-668"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>NonTermination</span>
<a name="line-669"></a> <span class='hs-comment'>-- ^The current thread is stuck in an infinite loop. This</span>
<a name="line-670"></a> <span class='hs-comment'>-- exception may or may not be thrown when the program is</span>
<a name="line-671"></a> <span class='hs-comment'>-- non-terminating.</span>
<a name="line-672"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>PatternMatchFail</span> <span class='hs-conid'>String</span>
<a name="line-673"></a> <span class='hs-comment'>-- ^A pattern matching failure. The 'String' argument should contain a</span>
<a name="line-674"></a> <span class='hs-comment'>-- descriptive message including the function name, source file</span>
<a name="line-675"></a> <span class='hs-comment'>-- and line number.</span>
<a name="line-676"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>RecConError</span> <span class='hs-conid'>String</span>
<a name="line-677"></a> <span class='hs-comment'>-- ^An attempt was made to evaluate a field of a record</span>
<a name="line-678"></a> <span class='hs-comment'>-- for which no value was given at construction time. The</span>
<a name="line-679"></a> <span class='hs-comment'>-- 'String' argument gives the location of the</span>
<a name="line-680"></a> <span class='hs-comment'>-- record construction in the source program.</span>
<a name="line-681"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>RecSelError</span> <span class='hs-conid'>String</span>
<a name="line-682"></a> <span class='hs-comment'>-- ^A field selection was attempted on a constructor that</span>
<a name="line-683"></a> <span class='hs-comment'>-- doesn\'t have the requested field. This can happen with</span>
<a name="line-684"></a> <span class='hs-comment'>-- multi-constructor records when one or more fields are</span>
<a name="line-685"></a> <span class='hs-comment'>-- missing from some of the constructors. The</span>
<a name="line-686"></a> <span class='hs-comment'>-- 'String' argument gives the location of the</span>
<a name="line-687"></a> <span class='hs-comment'>-- record selection in the source program.</span>
<a name="line-688"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>RecUpdError</span> <span class='hs-conid'>String</span>
<a name="line-689"></a> <span class='hs-comment'>-- ^An attempt was made to update a field in a record,</span>
<a name="line-690"></a> <span class='hs-comment'>-- where the record doesn\'t have the requested field. This can</span>
<a name="line-691"></a> <span class='hs-comment'>-- only occur with multi-constructor records, when one or more</span>
<a name="line-692"></a> <span class='hs-comment'>-- fields are missing from some of the constructors. The</span>
<a name="line-693"></a> <span class='hs-comment'>-- 'String' argument gives the location of the</span>
<a name="line-694"></a> <span class='hs-comment'>-- record update in the source program.</span>
<a name="line-695"></a><span class='hs-conid'>INSTANCE_TYPEABLE0</span><span class='hs-layout'>(</span><span class='hs-conid'>Exception</span><span class='hs-layout'>,</span><span class='hs-varid'>exceptionTc</span><span class='hs-layout'>,</span><span class='hs-str'>"Exception"</span><span class='hs-layout'>)</span>
<a name="line-696"></a>
<a name="line-697"></a><a name="Caster"></a><span class='hs-comment'>-- helper type for simplifying the type casting logic below</span>
<a name="line-698"></a><a name="Caster"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Caster</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'>New</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'>Caster</span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Exception</span><span class='hs-layout'>)</span>
<a name="line-699"></a>
<a name="line-700"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span> <span class='hs-conid'>Exception</span> <span class='hs-keyword'>where</span>
<a name="line-701"></a> <span class='hs-comment'>-- We need to collect all the sorts of exceptions that used to be</span>
<a name="line-702"></a> <span class='hs-comment'>-- bundled up into the Exception type, and rebundle them for</span>
<a name="line-703"></a> <span class='hs-comment'>-- legacy handlers.</span>
<a name="line-704"></a> <span class='hs-varid'>fromException</span> <span class='hs-varid'>exc0</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldr</span> <span class='hs-varid'>tryCast</span> <span class='hs-conid'>Nothing</span> <span class='hs-varid'>casters</span> <span class='hs-keyword'>where</span>
<a name="line-705"></a> <span class='hs-varid'>tryCast</span> <span class='hs-layout'>(</span><span class='hs-conid'>Caster</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</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-varid'>exc0</span> <span class='hs-keyword'>of</span>
<a name="line-706"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>exc</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span>
<a name="line-707"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>e</span>
<a name="line-708"></a> <span class='hs-varid'>casters</span> <span class='hs-keyglyph'>=</span>
<a name="line-709"></a> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>exc</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ArithException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-710"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>exc</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ArrayException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-711"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>New</span><span class='hs-varop'>.</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-conid'>AssertionFailed</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-712"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>exc</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AsyncException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-713"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedIndefinitelyOnMVar</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>BlockedOnDeadMVar</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-714"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedIndefinitelyOnSTM</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>BlockedIndefinitely</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-715"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>NestedAtomically</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>NestedAtomically</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-716"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>Deadlock</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Deadlock</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-717"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>exc</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>DynException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-718"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>New</span><span class='hs-varop'>.</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-conid'>ErrorCall</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-719"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>exc</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ExitException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-720"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>exc</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IOException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-721"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-722"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>NonTermination</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>NonTermination</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-723"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-724"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>RecConError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>RecConError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-725"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>RecSelError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>RecSelError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-726"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-727"></a> <span class='hs-comment'>-- Anything else gets taken as a Dynamic exception. It's</span>
<a name="line-728"></a> <span class='hs-comment'>-- important that we put all exceptions into the old Exception</span>
<a name="line-729"></a> <span class='hs-comment'>-- type somehow, or throwing a new exception wouldn't cause</span>
<a name="line-730"></a> <span class='hs-comment'>-- the cleanup code for bracket, finally etc to happen.</span>
<a name="line-731"></a> <span class='hs-conid'>Caster</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>exc</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>DynException</span> <span class='hs-layout'>(</span><span class='hs-varid'>toDyn</span> <span class='hs-layout'>(</span><span class='hs-varid'>exc</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>SomeException</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-keyglyph'>]</span>
<a name="line-732"></a>
<a name="line-733"></a> <span class='hs-comment'>-- Unbundle exceptions.</span>
<a name="line-734"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>ArithException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-varid'>exc</span>
<a name="line-735"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>ArrayException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-varid'>exc</span>
<a name="line-736"></a> <span class='hs-varid'>toException</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'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>AssertionFailed</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span>
<a name="line-737"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>AsyncException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-varid'>exc</span>
<a name="line-738"></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-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedIndefinitelyOnMVar</span>
<a name="line-739"></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'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedIndefinitelyOnSTM</span>
<a name="line-740"></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'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>NestedAtomically</span>
<a name="line-741"></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'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>Deadlock</span>
<a name="line-742"></a> <span class='hs-comment'>-- If a dynamic exception is a SomeException then resurrect it, so</span>
<a name="line-743"></a> <span class='hs-comment'>-- that bracket, catch+throw etc rethrow the same exception even</span>
<a name="line-744"></a> <span class='hs-comment'>-- when the exception is in the new style.</span>
<a name="line-745"></a> <span class='hs-comment'>-- If it's not a SomeException, then just throw the Dynamic.</span>
<a name="line-746"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>DynException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>fromDynamic</span> <span class='hs-varid'>exc</span> <span class='hs-keyword'>of</span>
<a name="line-747"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>exc'</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>exc'</span>
<a name="line-748"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>toException</span> <span class='hs-varid'>exc</span>
<a name="line-749"></a> <span class='hs-varid'>toException</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'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span>
<a name="line-750"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>ExitException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-varid'>exc</span>
<a name="line-751"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>IOException</span> <span class='hs-varid'>exc</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toException</span> <span class='hs-varid'>exc</span>
<a name="line-752"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>err</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'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span>
<a name="line-753"></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'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>NonTermination</span>
<a name="line-754"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>err</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'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span>
<a name="line-755"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecConError</span> <span class='hs-varid'>err</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'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>RecConError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span>
<a name="line-756"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecSelError</span> <span class='hs-varid'>err</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'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>RecSelError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span>
<a name="line-757"></a> <span class='hs-varid'>toException</span> <span class='hs-layout'>(</span><span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>err</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'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span>
<a name="line-758"></a>
<a name="line-759"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>Exception</span> <span class='hs-keyword'>where</span>
<a name="line-760"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>IOException</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>shows</span> <span class='hs-varid'>err</span>
<a name="line-761"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>ArithException</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>shows</span> <span class='hs-varid'>err</span>
<a name="line-762"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>ArrayException</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>shows</span> <span class='hs-varid'>err</span>
<a name="line-763"></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-764"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>ExitException</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-str'>"exit: "</span> <span class='hs-varop'>.</span> <span class='hs-varid'>shows</span> <span class='hs-varid'>err</span>
<a name="line-765"></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'>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-766"></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'>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-767"></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'>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-768"></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'>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-769"></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'>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-770"></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-771"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>DynException</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-str'>"exception :: "</span> <span class='hs-varop'>.</span> <span class='hs-varid'>showsTypeRep</span> <span class='hs-layout'>(</span><span class='hs-varid'>dynTypeRep</span> <span class='hs-varid'>err</span><span class='hs-layout'>)</span>
<a name="line-772"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>AsyncException</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>shows</span> <span class='hs-varid'>e</span>
<a name="line-773"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>BlockedOnDeadMVar</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedIndefinitelyOnMVar</span>
<a name="line-774"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>BlockedIndefinitely</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>BlockedIndefinitelyOnSTM</span>
<a name="line-775"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>NestedAtomically</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>NestedAtomically</span>
<a name="line-776"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>NonTermination</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>NonTermination</span>
<a name="line-777"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>Deadlock</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>p</span> <span class='hs-conid'>New</span><span class='hs-varop'>.</span><span class='hs-conid'>Deadlock</span>
<a name="line-778"></a>
<a name="line-779"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Eq</span> <span class='hs-conid'>Exception</span> <span class='hs-keyword'>where</span>
<a name="line-780"></a> <span class='hs-conid'>IOException</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>IOException</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-781"></a> <span class='hs-conid'>ArithException</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>ArithException</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-782"></a> <span class='hs-conid'>ArrayException</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>ArrayException</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-783"></a> <span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-784"></a> <span class='hs-conid'>ExitException</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>ExitException</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-785"></a> <span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>NoMethodError</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-786"></a> <span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>PatternMatchFail</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-787"></a> <span class='hs-conid'>RecSelError</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>RecSelError</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-788"></a> <span class='hs-conid'>RecConError</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>RecConError</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-789"></a> <span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>RecUpdError</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-790"></a> <span class='hs-conid'>AssertionFailed</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>AssertionFailed</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-791"></a> <span class='hs-conid'>DynException</span> <span class='hs-keyword'>_</span> <span class='hs-varop'>==</span> <span class='hs-conid'>DynException</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>False</span> <span class='hs-comment'>-- incomparable</span>
<a name="line-792"></a> <span class='hs-conid'>AsyncException</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-conid'>AsyncException</span> <span class='hs-varid'>e2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>e1</span> <span class='hs-varop'>==</span> <span class='hs-varid'>e2</span>
<a name="line-793"></a> <span class='hs-conid'>BlockedOnDeadMVar</span> <span class='hs-varop'>==</span> <span class='hs-conid'>BlockedOnDeadMVar</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>True</span>
<a name="line-794"></a> <span class='hs-conid'>NonTermination</span> <span class='hs-varop'>==</span> <span class='hs-conid'>NonTermination</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>True</span>
<a name="line-795"></a> <span class='hs-conid'>NestedAtomically</span> <span class='hs-varop'>==</span> <span class='hs-conid'>NestedAtomically</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>True</span>
<a name="line-796"></a> <span class='hs-conid'>Deadlock</span> <span class='hs-varop'>==</span> <span class='hs-conid'>Deadlock</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>True</span>
<a name="line-797"></a> <span class='hs-keyword'>_</span> <span class='hs-varop'>==</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>False</span>
<a name="line-798"></a>
</pre></body>
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