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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE UndecidableInstances #-}</span>
<a name="line-2"></a><span class='hs-comment'>-- Search for UndecidableInstances to see why this is needed</span>
<a name="line-3"></a>
<a name="line-4"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-5"></a><span class='hs-comment'>-- |</span>
<a name="line-6"></a><span class='hs-comment'>-- Module : Control.Monad.Writer.Class</span>
<a name="line-7"></a><span class='hs-comment'>-- Copyright : (c) Andy Gill 2001,</span>
<a name="line-8"></a><span class='hs-comment'>-- (c) Oregon Graduate Institute of Science and Technology, 2001</span>
<a name="line-9"></a><span class='hs-comment'>-- License : BSD-style (see the file 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 (multi-param classes, functional dependencies)</span>
<a name="line-14"></a><span class='hs-comment'>--</span>
<a name="line-15"></a><span class='hs-comment'>-- The MonadWriter class.</span>
<a name="line-16"></a><span class='hs-comment'>--</span>
<a name="line-17"></a><span class='hs-comment'>-- Inspired by the paper</span>
<a name="line-18"></a><span class='hs-comment'>-- /Functional Programming with Overloading and Higher-Order Polymorphism/,</span>
<a name="line-19"></a><span class='hs-comment'>-- Mark P Jones (<<a href="http://web.cecs.pdx.edu/~mpj/pubs/springschool.html">http://web.cecs.pdx.edu/~mpj/pubs/springschool.html</a>>)</span>
<a name="line-20"></a><span class='hs-comment'>-- Advanced School of Functional Programming, 1995.</span>
<a name="line-21"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-22"></a>
<a name="line-23"></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'>Writer</span><span class='hs-varop'>.</span><span class='hs-conid'>Class</span> <span class='hs-layout'>(</span>
<a name="line-24"></a> <span class='hs-conid'>MonadWriter</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-25"></a> <span class='hs-varid'>listens</span><span class='hs-layout'>,</span>
<a name="line-26"></a> <span class='hs-varid'>censor</span><span class='hs-layout'>,</span>
<a name="line-27"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-28"></a>
<a name="line-29"></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'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Error</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Error</span>
<a name="line-30"></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'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Identity</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Identity</span>
<a name="line-31"></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'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Maybe</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Maybe</span>
<a name="line-32"></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'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Reader</span>
<a name="line-33"></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'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>RWS</span><span class='hs-varop'>.</span><span class='hs-conid'>Lazy</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>LazyRWS</span> <span class='hs-layout'>(</span>
<a name="line-34"></a> <span class='hs-conid'>RWST</span><span class='hs-layout'>,</span> <span class='hs-varid'>tell</span><span class='hs-layout'>,</span> <span class='hs-varid'>listen</span><span class='hs-layout'>,</span> <span class='hs-varid'>pass</span><span class='hs-layout'>)</span>
<a name="line-35"></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'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>RWS</span><span class='hs-varop'>.</span><span class='hs-conid'>Strict</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>StrictRWS</span> <span class='hs-layout'>(</span>
<a name="line-36"></a> <span class='hs-conid'>RWST</span><span class='hs-layout'>,</span> <span class='hs-varid'>tell</span><span class='hs-layout'>,</span> <span class='hs-varid'>listen</span><span class='hs-layout'>,</span> <span class='hs-varid'>pass</span><span class='hs-layout'>)</span>
<a name="line-37"></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'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>State</span><span class='hs-varop'>.</span><span class='hs-conid'>Lazy</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Lazy</span>
<a name="line-38"></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'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>State</span><span class='hs-varop'>.</span><span class='hs-conid'>Strict</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Strict</span>
<a name="line-39"></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'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Writer</span><span class='hs-varop'>.</span><span class='hs-conid'>Lazy</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Lazy</span> <span class='hs-layout'>(</span>
<a name="line-40"></a> <span class='hs-conid'>WriterT</span><span class='hs-layout'>,</span> <span class='hs-varid'>tell</span><span class='hs-layout'>,</span> <span class='hs-varid'>listen</span><span class='hs-layout'>,</span> <span class='hs-varid'>pass</span><span class='hs-layout'>)</span>
<a name="line-41"></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'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Writer</span><span class='hs-varop'>.</span><span class='hs-conid'>Strict</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Strict</span> <span class='hs-layout'>(</span>
<a name="line-42"></a> <span class='hs-conid'>WriterT</span><span class='hs-layout'>,</span> <span class='hs-varid'>tell</span><span class='hs-layout'>,</span> <span class='hs-varid'>listen</span><span class='hs-layout'>,</span> <span class='hs-varid'>pass</span><span class='hs-layout'>)</span>
<a name="line-43"></a>
<a name="line-44"></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'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Class</span> <span class='hs-layout'>(</span><span class='hs-varid'>lift</span><span class='hs-layout'>)</span>
<a name="line-45"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span>
<a name="line-46"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Monoid</span>
<a name="line-47"></a>
<a name="line-48"></a><span class='hs-comment'>-- ---------------------------------------------------------------------------</span>
<a name="line-49"></a><span class='hs-comment'>-- MonadWriter class</span>
<a name="line-50"></a><span class='hs-comment'>--</span>
<a name="line-51"></a><span class='hs-comment'>-- tell is like tell on the MUD's it shouts to monad</span>
<a name="line-52"></a><span class='hs-comment'>-- what you want to be heard. The monad carries this 'packet'</span>
<a name="line-53"></a><span class='hs-comment'>-- upwards, merging it if needed (hence the Monoid requirement).</span>
<a name="line-54"></a><span class='hs-comment'>--</span>
<a name="line-55"></a><span class='hs-comment'>-- listen listens to a monad acting, and returns what the monad "said".</span>
<a name="line-56"></a><span class='hs-comment'>--</span>
<a name="line-57"></a><span class='hs-comment'>-- pass lets you provide a writer transformer which changes internals of</span>
<a name="line-58"></a><span class='hs-comment'>-- the written object.</span>
<a name="line-59"></a>
<a name="line-60"></a><a name="MonadWriter"></a><span class='hs-keyword'>class</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monoid</span> <span class='hs-varid'>w</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-keyglyph'>=></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-varid'>m</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>w</span> <span class='hs-keyword'>where</span>
<a name="line-61"></a> <span class='hs-comment'>-- | @'tell' w@ is an action that produces the output @w@.</span>
<a name="line-62"></a> <span class='hs-varid'>tell</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>w</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span>
<a name="line-63"></a> <span class='hs-comment'>-- | @'listen' m@ is an action that executes the action @m@ and adds</span>
<a name="line-64"></a> <span class='hs-comment'>-- its output to the value of the computation.</span>
<a name="line-65"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <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>
<a name="line-66"></a> <span class='hs-comment'>-- | @'pass' m@ is an action that executes the action @m@, which</span>
<a name="line-67"></a> <span class='hs-comment'>-- returns a value and a function, and returns the value, applying</span>
<a name="line-68"></a> <span class='hs-comment'>-- the function to the output.</span>
<a name="line-69"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>m</span> <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-keyglyph'>-></span> <span class='hs-varid'>w</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span>
<a name="line-70"></a>
<a name="line-71"></a><a name="listens"></a><span class='hs-comment'>-- | @'listens' f m@ is an action that executes the action @m@ and adds</span>
<a name="line-72"></a><span class='hs-comment'>-- the result of applying @f@ to the output to the value of the computation.</span>
<a name="line-73"></a><span class='hs-comment'>--</span>
<a name="line-74"></a><span class='hs-comment'>-- * @'listens' f m = 'liftM' (id *** f) ('listen' m)@</span>
<a name="line-75"></a><span class='hs-definition'>listens</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-varid'>w</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-76"></a><span class='hs-definition'>listens</span> <span class='hs-varid'>f</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-77"></a> <span class='hs-keyglyph'>~</span><span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>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-78"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>f</span> <span class='hs-varid'>w</span><span class='hs-layout'>)</span>
<a name="line-79"></a>
<a name="line-80"></a><a name="censor"></a><span class='hs-comment'>-- | @'censor' f m@ is an action that executes the action @m@ and</span>
<a name="line-81"></a><span class='hs-comment'>-- applies the function @f@ to its output, leaving the return value</span>
<a name="line-82"></a><span class='hs-comment'>-- unchanged.</span>
<a name="line-83"></a><span class='hs-comment'>--</span>
<a name="line-84"></a><span class='hs-comment'>-- * @'censor' f m = 'pass' ('liftM' (\\x -> (x,f)) m)@</span>
<a name="line-85"></a><span class='hs-definition'>censor</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-varid'>w</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>w</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span>
<a name="line-86"></a><span class='hs-definition'>censor</span> <span class='hs-varid'>f</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-87"></a> <span class='hs-varid'>a</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>m</span>
<a name="line-88"></a> <span class='hs-varid'>return</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-89"></a>
<a name="line-90"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monoid</span> <span class='hs-varid'>w</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-keyglyph'>=></span> <span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-layout'>(</span><span class='hs-conid'>Lazy</span><span class='hs-varop'>.</span><span class='hs-conid'>WriterT</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-91"></a> <span class='hs-varid'>tell</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Lazy</span><span class='hs-varop'>.</span><span class='hs-varid'>tell</span>
<a name="line-92"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Lazy</span><span class='hs-varop'>.</span><span class='hs-varid'>listen</span>
<a name="line-93"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Lazy</span><span class='hs-varop'>.</span><span class='hs-varid'>pass</span>
<a name="line-94"></a>
<a name="line-95"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monoid</span> <span class='hs-varid'>w</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-keyglyph'>=></span> <span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-layout'>(</span><span class='hs-conid'>Strict</span><span class='hs-varop'>.</span><span class='hs-conid'>WriterT</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-96"></a> <span class='hs-varid'>tell</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Strict</span><span class='hs-varop'>.</span><span class='hs-varid'>tell</span>
<a name="line-97"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Strict</span><span class='hs-varop'>.</span><span class='hs-varid'>listen</span>
<a name="line-98"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Strict</span><span class='hs-varop'>.</span><span class='hs-varid'>pass</span>
<a name="line-99"></a>
<a name="line-100"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monoid</span> <span class='hs-varid'>w</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-keyglyph'>=></span> <span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-layout'>(</span><span class='hs-conid'>LazyRWS</span><span class='hs-varop'>.</span><span class='hs-conid'>RWST</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-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-101"></a> <span class='hs-varid'>tell</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>LazyRWS</span><span class='hs-varop'>.</span><span class='hs-varid'>tell</span>
<a name="line-102"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>LazyRWS</span><span class='hs-varop'>.</span><span class='hs-varid'>listen</span>
<a name="line-103"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>LazyRWS</span><span class='hs-varop'>.</span><span class='hs-varid'>pass</span>
<a name="line-104"></a>
<a name="line-105"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monoid</span> <span class='hs-varid'>w</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-keyglyph'>=></span> <span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-layout'>(</span><span class='hs-conid'>StrictRWS</span><span class='hs-varop'>.</span><span class='hs-conid'>RWST</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-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-106"></a> <span class='hs-varid'>tell</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StrictRWS</span><span class='hs-varop'>.</span><span class='hs-varid'>tell</span>
<a name="line-107"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StrictRWS</span><span class='hs-varop'>.</span><span class='hs-varid'>listen</span>
<a name="line-108"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StrictRWS</span><span class='hs-varop'>.</span><span class='hs-varid'>pass</span>
<a name="line-109"></a>
<a name="line-110"></a><span class='hs-comment'>-- ---------------------------------------------------------------------------</span>
<a name="line-111"></a><span class='hs-comment'>-- Instances for other mtl transformers</span>
<a name="line-112"></a><span class='hs-comment'>--</span>
<a name="line-113"></a><span class='hs-comment'>-- All of these instances need UndecidableInstances,</span>
<a name="line-114"></a><span class='hs-comment'>-- because they do not satisfy the coverage condition.</span>
<a name="line-115"></a>
<a name="line-116"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Error</span> <span class='hs-varid'>e</span><span class='hs-layout'>,</span> <span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</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'>ErrorT</span> <span class='hs-varid'>e</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-117"></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-118"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Error</span><span class='hs-varop'>.</span><span class='hs-varid'>liftListen</span> <span class='hs-varid'>listen</span>
<a name="line-119"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Error</span><span class='hs-varop'>.</span><span class='hs-varid'>liftPass</span> <span class='hs-varid'>pass</span>
<a name="line-120"></a>
<a name="line-121"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</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'>IdentityT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-122"></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-123"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Identity</span><span class='hs-varop'>.</span><span class='hs-varid'>mapIdentityT</span> <span class='hs-varid'>listen</span>
<a name="line-124"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Identity</span><span class='hs-varop'>.</span><span class='hs-varid'>mapIdentityT</span> <span class='hs-varid'>pass</span>
<a name="line-125"></a>
<a name="line-126"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</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'>MaybeT</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-127"></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-128"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Maybe</span><span class='hs-varop'>.</span><span class='hs-varid'>liftListen</span> <span class='hs-varid'>listen</span>
<a name="line-129"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Maybe</span><span class='hs-varop'>.</span><span class='hs-varid'>liftPass</span> <span class='hs-varid'>pass</span>
<a name="line-130"></a>
<a name="line-131"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</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'>ReaderT</span> <span class='hs-varid'>r</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-132"></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-133"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mapReaderT</span> <span class='hs-varid'>listen</span>
<a name="line-134"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mapReaderT</span> <span class='hs-varid'>pass</span>
<a name="line-135"></a>
<a name="line-136"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</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'>Lazy</span><span class='hs-varop'>.</span><span class='hs-conid'>StateT</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-137"></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-138"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Lazy</span><span class='hs-varop'>.</span><span class='hs-varid'>liftListen</span> <span class='hs-varid'>listen</span>
<a name="line-139"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Lazy</span><span class='hs-varop'>.</span><span class='hs-varid'>liftPass</span> <span class='hs-varid'>pass</span>
<a name="line-140"></a>
<a name="line-141"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>MonadWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</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'>Strict</span><span class='hs-varop'>.</span><span class='hs-conid'>StateT</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-142"></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-143"></a> <span class='hs-varid'>listen</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Strict</span><span class='hs-varop'>.</span><span class='hs-varid'>liftListen</span> <span class='hs-varid'>listen</span>
<a name="line-144"></a> <span class='hs-varid'>pass</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Strict</span><span class='hs-varop'>.</span><span class='hs-varid'>liftPass</span> <span class='hs-varid'>pass</span>
</pre></body>
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