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<title>src/Control/Monad/Catch/Pure.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE CPP #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-# LANGUAGE ExistentialQuantification #-}</span>
<a name="line-3"></a><span class='hs-comment'>{-# LANGUAGE GeneralizedNewtypeDeriving #-}</span>
<a name="line-4"></a><span class='hs-comment'>{-# LANGUAGE RankNTypes #-}</span>
<a name="line-5"></a><span class='hs-comment'>{-# LANGUAGE FlexibleInstances #-}</span>
<a name="line-6"></a><span class='hs-comment'>{-# LANGUAGE MultiParamTypeClasses #-}</span>
<a name="line-7"></a><span class='hs-comment'>{-# LANGUAGE UndecidableInstances #-}</span>
<a name="line-8"></a>
<a name="line-9"></a><span class='hs-cpp'>#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 702</span>
<a name="line-10"></a><span class='hs-comment'>{-# LANGUAGE Trustworthy #-}</span>
<a name="line-11"></a><span class='hs-cpp'>#endif</span>
<a name="line-12"></a>
<a name="line-13"></a><span class='hs-cpp'>#ifndef MIN_VERSION_transformers</span>
<a name="line-14"></a><span class='hs-cpp'>#define MIN_VERSION_transformers(x,y,z) 1</span>
<a name="line-15"></a><span class='hs-cpp'>#endif</span>
<a name="line-16"></a>
<a name="line-17"></a><span class='hs-cpp'>#ifndef MIN_VERSION_mtl</span>
<a name="line-18"></a><span class='hs-cpp'>#define MIN_VERSION_mtl(x,y,z) 1</span>
<a name="line-19"></a><span class='hs-cpp'>#endif</span>
<a name="line-20"></a>
<a name="line-21"></a><span class='hs-comment'>--------------------------------------------------------------------</span>
<a name="line-22"></a><span class='hs-comment'>-- |</span>
<a name="line-23"></a><span class='hs-comment'>-- Copyright : (C) Edward Kmett 2013-2015, (c) Google Inc. 2012</span>
<a name="line-24"></a><span class='hs-comment'>-- License : BSD-style (see the file LICENSE)</span>
<a name="line-25"></a><span class='hs-comment'>-- Maintainer : Edward Kmett <ekmett@gmail.com></span>
<a name="line-26"></a><span class='hs-comment'>-- Stability : experimental</span>
<a name="line-27"></a><span class='hs-comment'>-- Portability : non-portable</span>
<a name="line-28"></a><span class='hs-comment'>--</span>
<a name="line-29"></a><span class='hs-comment'>-- This module supplies a \'pure\' monad transformer that can be used for</span>
<a name="line-30"></a><span class='hs-comment'>-- mock-testing code that throws exceptions, so long as those exceptions</span>
<a name="line-31"></a><span class='hs-comment'>-- are always thrown with 'throwM'.</span>
<a name="line-32"></a><span class='hs-comment'>--</span>
<a name="line-33"></a><span class='hs-comment'>-- Do not mix 'CatchT' with 'IO'. Choose one or the other for the</span>
<a name="line-34"></a><span class='hs-comment'>-- bottom of your transformer stack!</span>
<a name="line-35"></a><span class='hs-comment'>--------------------------------------------------------------------</span>
<a name="line-36"></a>
<a name="line-37"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Catch</span><span class='hs-varop'>.</span><span class='hs-conid'>Pure</span> <span class='hs-layout'>(</span>
<a name="line-38"></a> <span class='hs-comment'>-- * Transformer</span>
<a name="line-39"></a> <span class='hs-comment'>-- $transformer</span>
<a name="line-40"></a> <span class='hs-conid'>CatchT</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>Catch</span>
<a name="line-41"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>runCatch</span>
<a name="line-42"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>mapCatchT</span>
<a name="line-43"></a>
<a name="line-44"></a> <span class='hs-comment'>-- * Typeclass</span>
<a name="line-45"></a> <span class='hs-comment'>-- $mtl</span>
<a name="line-46"></a> <span class='hs-layout'>,</span> <span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Catch</span>
<a name="line-47"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-48"></a>
<a name="line-49"></a><span class='hs-cpp'>#if defined(__GLASGOW_HASKELL__) && (__GLASGOW_HASKELL__ >= 706)</span>
<a name="line-50"></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'>foldr</span><span class='hs-layout'>)</span>
<a name="line-51"></a><span class='hs-cpp'>#else</span>
<a name="line-52"></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> <span class='hs-varid'>foldr</span><span class='hs-layout'>)</span>
<a name="line-53"></a><span class='hs-cpp'>#endif</span>
<a name="line-54"></a>
<a name="line-55"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Applicative</span>
<a name="line-56"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Catch</span>
<a name="line-57"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Reader</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Reader</span>
<a name="line-58"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>RWS</span>
<a name="line-59"></a><span class='hs-cpp'>#if __GLASGOW_HASKELL__ < 710</span>
<a name="line-60"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Foldable</span>
<a name="line-61"></a><span class='hs-cpp'>#endif</span>
<a name="line-62"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Functor</span><span class='hs-varop'>.</span><span class='hs-conid'>Identity</span>
<a name="line-63"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Traversable</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Traversable</span>
<a name="line-64"></a>
<a name="line-65"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-66"></a><span class='hs-comment'>-- $mtl</span>
<a name="line-67"></a><span class='hs-comment'>-- The mtl style typeclass</span>
<a name="line-68"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-69"></a>
<a name="line-70"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-71"></a><span class='hs-comment'>-- $transformer</span>
<a name="line-72"></a><span class='hs-comment'>-- The @transformers@-style monad transfomer</span>
<a name="line-73"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-74"></a>
<a name="line-75"></a><span class='hs-comment'>-- | Add 'Exception' handling abilities to a 'Monad'.</span>
<a name="line-76"></a><span class='hs-comment'>--</span>
<a name="line-77"></a><span class='hs-comment'>-- This should /never/ be used in combination with 'IO'. Think of 'CatchT'</span>
<a name="line-78"></a><span class='hs-comment'>-- as an alternative base monad for use with mocking code that solely throws</span>
<a name="line-79"></a><span class='hs-comment'>-- exceptions via 'throwM'.</span>
<a name="line-80"></a><span class='hs-comment'>--</span>
<a name="line-81"></a><span class='hs-comment'>-- Note: that 'IO' monad has these abilities already, so stacking 'CatchT' on top</span>
<a name="line-82"></a><span class='hs-comment'>-- of it does not add any value and can possibly be confusing:</span>
<a name="line-83"></a><span class='hs-comment'>--</span>
<a name="line-84"></a><span class='hs-comment'>-- >>> (error "Hello!" :: IO ()) `catch` (\(e :: ErrorCall) -> liftIO $ print e)</span>
<a name="line-85"></a><span class='hs-comment'>-- Hello!</span>
<a name="line-86"></a><span class='hs-comment'>--</span>
<a name="line-87"></a><span class='hs-comment'>-- >>> runCatchT $ (error "Hello!" :: CatchT IO ()) `catch` (\(e :: ErrorCall) -> liftIO $ print e)</span>
<a name="line-88"></a><span class='hs-comment'>-- *** Exception: Hello!</span>
<a name="line-89"></a><span class='hs-comment'>--</span>
<a name="line-90"></a><span class='hs-comment'>-- >>> runCatchT $ (throwM (ErrorCall "Hello!") :: CatchT IO ()) `catch` (\(e :: ErrorCall) -> liftIO $ print e)</span>
<a name="line-91"></a><span class='hs-comment'>-- Hello!</span>
<a name="line-92"></a>
<a name="line-93"></a><a name="CatchT"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-layout'>{</span> <span class='hs-varid'>runCatchT</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>Either</span> <span class='hs-conid'>SomeException</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-layout'>}</span>
<a name="line-94"></a>
<a name="line-95"></a><a name="Catch"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>Catch</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-conid'>Identity</span>
<a name="line-96"></a>
<a name="line-97"></a><a name="runCatch"></a><span class='hs-definition'>runCatch</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Catch</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Either</span> <span class='hs-conid'>SomeException</span> <span class='hs-varid'>a</span>
<a name="line-98"></a><span class='hs-definition'>runCatch</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>runIdentity</span> <span class='hs-varop'>.</span> <span class='hs-varid'>runCatchT</span>
<a name="line-99"></a>
<a name="line-100"></a><a name="instance%20Functor%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Functor</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-101"></a> <span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-layout'>(</span><span class='hs-varid'>liftM</span> <span class='hs-layout'>(</span><span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span>
<a name="line-102"></a>
<a name="line-103"></a><a name="instance%20Applicative%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Applicative</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-104"></a> <span class='hs-varid'>pure</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-layout'>(</span><span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-105"></a> <span class='hs-layout'>(</span><span class='hs-varop'><*></span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ap</span>
<a name="line-106"></a>
<a name="line-107"></a><a name="instance%20Monad%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Monad</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-108"></a> <span class='hs-varid'>return</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>pure</span>
<a name="line-109"></a> <span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span> <span class='hs-varop'>>>=</span> <span class='hs-varid'>k</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>$</span> <span class='hs-varid'>m</span> <span class='hs-varop'>>>=</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>ea</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>ea</span> <span class='hs-keyword'>of</span>
<a name="line-110"></a> <span class='hs-conid'>Left</span> <span class='hs-varid'>e</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span>
<a name="line-111"></a> <span class='hs-conid'>Right</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>runCatchT</span> <span class='hs-layout'>(</span><span class='hs-varid'>k</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-112"></a> <span class='hs-varid'>fail</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>.</span> <span class='hs-varid'>return</span> <span class='hs-varop'>.</span> <span class='hs-conid'>Left</span> <span class='hs-varop'>.</span> <span class='hs-varid'>toException</span> <span class='hs-varop'>.</span> <span class='hs-varid'>userError</span>
<a name="line-113"></a>
<a name="line-114"></a><a name="instance%20MonadFix%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>MonadFix</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadFix</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-115"></a> <span class='hs-varid'>mfix</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>$</span> <span class='hs-varid'>mfix</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>runCatchT</span> <span class='hs-varop'>$</span> <span class='hs-varid'>f</span> <span class='hs-varop'>$</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>a</span> <span class='hs-keyword'>of</span>
<a name="line-116"></a> <span class='hs-conid'>Right</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>r</span>
<a name="line-117"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>error</span> <span class='hs-str'>"empty mfix argument"</span>
<a name="line-118"></a>
<a name="line-119"></a><a name="instance%20Foldable%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Foldable</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Foldable</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-120"></a> <span class='hs-varid'>foldMap</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldMap</span> <span class='hs-layout'>(</span><span class='hs-varid'>foldMapEither</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varid'>m</span> <span class='hs-keyword'>where</span>
<a name="line-121"></a> <span class='hs-varid'>foldMapEither</span> <span class='hs-varid'>g</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>g</span> <span class='hs-varid'>a</span>
<a name="line-122"></a> <span class='hs-varid'>foldMapEither</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mempty</span>
<a name="line-123"></a>
<a name="line-124"></a><a name="instance%20Traversable%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Traversable</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Traversable</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-125"></a> <span class='hs-varid'>traverse</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'><$></span> <span class='hs-conid'>Traversable</span><span class='hs-varop'>.</span><span class='hs-varid'>traverse</span> <span class='hs-layout'>(</span><span class='hs-varid'>traverseEither</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varid'>m</span> <span class='hs-keyword'>where</span>
<a name="line-126"></a> <span class='hs-varid'>traverseEither</span> <span class='hs-varid'>g</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Right</span> <span class='hs-varop'><$></span> <span class='hs-varid'>g</span> <span class='hs-varid'>a</span>
<a name="line-127"></a> <span class='hs-varid'>traverseEither</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>pure</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-varid'>e</span><span class='hs-layout'>)</span>
<a name="line-128"></a>
<a name="line-129"></a><a name="instance%20Alternative%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Alternative</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-130"></a> <span class='hs-varid'>empty</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mzero</span>
<a name="line-131"></a> <span class='hs-layout'>(</span><span class='hs-varop'><|></span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mplus</span>
<a name="line-132"></a>
<a name="line-133"></a><a name="instance%20MonadPlus%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadPlus</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-134"></a> <span class='hs-varid'>mzero</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>$</span> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Left</span> <span class='hs-varop'>$</span> <span class='hs-varid'>toException</span> <span class='hs-varop'>$</span> <span class='hs-varid'>userError</span> <span class='hs-str'>""</span>
<a name="line-135"></a> <span class='hs-varid'>mplus</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>n</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>$</span> <span class='hs-varid'>m</span> <span class='hs-varop'>>>=</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>ea</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>ea</span> <span class='hs-keyword'>of</span>
<a name="line-136"></a> <span class='hs-conid'>Left</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>n</span>
<a name="line-137"></a> <span class='hs-conid'>Right</span> <span class='hs-varid'>a</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'>a</span><span class='hs-layout'>)</span>
<a name="line-138"></a>
<a name="line-139"></a><a name="instance%20MonadTrans%20CatchT"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>MonadTrans</span> <span class='hs-conid'>CatchT</span> <span class='hs-keyword'>where</span>
<a name="line-140"></a> <span class='hs-varid'>lift</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>$</span> <span class='hs-keyword'>do</span>
<a name="line-141"></a> <span class='hs-varid'>a</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>m</span>
<a name="line-142"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Right</span> <span class='hs-varid'>a</span>
<a name="line-143"></a>
<a name="line-144"></a><a name="instance%20MonadIO%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>MonadIO</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadIO</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-145"></a> <span class='hs-varid'>liftIO</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>$</span> <span class='hs-keyword'>do</span>
<a name="line-146"></a> <span class='hs-varid'>a</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>liftIO</span> <span class='hs-varid'>m</span>
<a name="line-147"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Right</span> <span class='hs-varid'>a</span>
<a name="line-148"></a>
<a name="line-149"></a><a name="instance%20MonadThrow%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadThrow</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-150"></a> <span class='hs-varid'>throwM</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>.</span> <span class='hs-varid'>return</span> <span class='hs-varop'>.</span> <span class='hs-conid'>Left</span> <span class='hs-varop'>.</span> <span class='hs-varid'>toException</span>
<a name="line-151"></a><a name="instance%20MonadCatch%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadCatch</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-152"></a> <span class='hs-varid'>catch</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>$</span> <span class='hs-varid'>m</span> <span class='hs-varop'>>>=</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>ea</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>ea</span> <span class='hs-keyword'>of</span>
<a name="line-153"></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'>fromException</span> <span class='hs-varid'>e</span> <span class='hs-keyword'>of</span>
<a name="line-154"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>e'</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>runCatchT</span> <span class='hs-layout'>(</span><span class='hs-varid'>c</span> <span class='hs-varid'>e'</span><span class='hs-layout'>)</span>
<a name="line-155"></a> <span class='hs-conid'>Nothing</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>
<a name="line-156"></a> <span class='hs-conid'>Right</span> <span class='hs-varid'>a</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'>a</span><span class='hs-layout'>)</span>
<a name="line-157"></a><a name="instance%20MonadMask%20(CatchT%20m)"></a><span class='hs-comment'>-- | Note: This instance is only valid if the underlying monad has a single</span>
<a name="line-158"></a><a name="instance%20MonadMask%20(CatchT%20m)"></a><span class='hs-comment'>-- exit point!</span>
<a name="line-159"></a><a name="instance%20MonadMask%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadMask</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-160"></a> <span class='hs-varid'>mask</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>a</span> <span class='hs-varid'>id</span>
<a name="line-161"></a> <span class='hs-varid'>uninterruptibleMask</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>a</span> <span class='hs-varid'>id</span>
<a name="line-162"></a>
<a name="line-163"></a><a name="instance%20MonadState%20s%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>MonadState</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadState</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-164"></a> <span class='hs-varid'>get</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varid'>get</span>
<a name="line-165"></a> <span class='hs-varid'>put</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varop'>.</span> <span class='hs-varid'>put</span>
<a name="line-166"></a><span class='hs-cpp'>#if MIN_VERSION_mtl(2,1,0)</span>
<a name="line-167"></a> <span class='hs-varid'>state</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varop'>.</span> <span class='hs-varid'>state</span>
<a name="line-168"></a><span class='hs-cpp'>#endif</span>
<a name="line-169"></a>
<a name="line-170"></a><a name="instance%20MonadReader%20e%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>MonadReader</span> <span class='hs-varid'>e</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadReader</span> <span class='hs-varid'>e</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-171"></a> <span class='hs-varid'>ask</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varid'>ask</span>
<a name="line-172"></a> <span class='hs-varid'>local</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-layout'>(</span><span class='hs-varid'>local</span> <span class='hs-varid'>f</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span>
<a name="line-173"></a>
<a name="line-174"></a><a name="instance%20MonadWriter%20w%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-175"></a> <span class='hs-varid'>tell</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varop'>.</span> <span class='hs-varid'>tell</span>
<a name="line-176"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mapCatchT</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>do</span>
<a name="line-177"></a> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>w</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>listen</span> <span class='hs-varid'>m</span>
<a name="line-178"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$!</span> <span class='hs-varid'>fmap</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>r</span><span class='hs-layout'>,</span> <span class='hs-varid'>w</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span>
<a name="line-179"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mapCatchT</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>pass</span> <span class='hs-varop'>$</span> <span class='hs-keyword'>do</span>
<a name="line-180"></a> <span class='hs-varid'>a</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>m</span>
<a name="line-181"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$!</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>a</span> <span class='hs-keyword'>of</span>
<a name="line-182"></a> <span class='hs-conid'>Left</span> <span class='hs-varid'>l</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-varid'>l</span><span class='hs-layout'>,</span> <span class='hs-varid'>id</span><span class='hs-layout'>)</span>
<a name="line-183"></a> <span class='hs-conid'>Right</span> <span class='hs-layout'>(</span><span class='hs-varid'>r</span><span class='hs-layout'>,</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varid'>r</span><span class='hs-layout'>,</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-184"></a><span class='hs-cpp'>#if MIN_VERSION_mtl(2,1,0)</span>
<a name="line-185"></a> <span class='hs-varid'>writer</span> <span class='hs-varid'>aw</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varop'>`liftM`</span> <span class='hs-varid'>writer</span> <span class='hs-varid'>aw</span><span class='hs-layout'>)</span>
<a name="line-186"></a><span class='hs-cpp'>#endif</span>
<a name="line-187"></a>
<a name="line-188"></a><a name="instance%20MonadRWS%20r%20w%20s%20(CatchT%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>MonadRWS</span> <span class='hs-varid'>r</span> <span class='hs-varid'>w</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadRWS</span> <span class='hs-varid'>r</span> <span class='hs-varid'>w</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span>
<a name="line-189"></a>
<a name="line-190"></a><a name="mapCatchT"></a><span class='hs-comment'>-- | Map the unwrapped computation using the given function.</span>
<a name="line-191"></a><span class='hs-comment'>--</span>
<a name="line-192"></a><span class='hs-comment'>-- @'runCatchT' ('mapCatchT' f m) = f ('runCatchT' m)@</span>
<a name="line-193"></a><span class='hs-definition'>mapCatchT</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>Either</span> <span class='hs-conid'>SomeException</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>n</span> <span class='hs-layout'>(</span><span class='hs-conid'>Either</span> <span class='hs-conid'>SomeException</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-194"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>CatchT</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span>
<a name="line-195"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>CatchT</span> <span class='hs-varid'>n</span> <span class='hs-varid'>b</span>
<a name="line-196"></a><span class='hs-definition'>mapCatchT</span> <span class='hs-varid'>f</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>CatchT</span> <span class='hs-varop'>$</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-varid'>runCatchT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span>
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