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<pre><a name="line-1"></a><span class='hs-comment'>{-|
<a name="line-2"></a> Compos compatibility layer. This module serves as a drop-in
<a name="line-3"></a> replacement in some situations for some of the Compos operations.
<a name="line-4"></a> Only the single-type traversals are supported, on normal
<a name="line-5"></a> algebraic data types. Users should also import either "Data.Generics.Uniplate.Data"
<a name="line-6"></a> or "Data.Generics.Uniplate.Direct".
<a name="line-7"></a>
<a name="line-8"></a> Compos is described in the paper: \"A Pattern for Almost Compositional Functions\"
<a name="line-9"></a> by Bjorn Bringert and Aarne Ranta.
<a name="line-10"></a>
<a name="line-11"></a> * <<a href="http://doi.acm.org/10.1145/1159803.1159834">http://doi.acm.org/10.1145/1159803.1159834</a>>
<a name="line-12"></a>
<a name="line-13"></a> * <<a href="http://www.cs.chalmers.se/~bringert/publ/composOp/composOp.pdf">http://www.cs.chalmers.se/~bringert/publ/composOp/composOp.pdf</a>>
<a name="line-14"></a>-}</span>
<a name="line-15"></a>
<a name="line-16"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Generics</span><span class='hs-varop'>.</span><span class='hs-conid'>Compos</span> <span class='hs-keyword'>where</span>
<a name="line-17"></a>
<a name="line-18"></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-19"></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-20"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Generics</span><span class='hs-varop'>.</span><span class='hs-conid'>Uniplate</span><span class='hs-varop'>.</span><span class='hs-conid'>Operations</span>
<a name="line-21"></a>
<a name="line-22"></a>
<a name="line-23"></a><a name="Compos"></a><span class='hs-comment'>-- | If you want to keep an existing type class</span>
<a name="line-24"></a><a name="Compos"></a><span class='hs-keyword'>class</span> <span class='hs-conid'>Uniplate</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Compos</span> <span class='hs-varid'>a</span> <span class='hs-keyword'>where</span>
<a name="line-25"></a>
<a name="line-26"></a>
<a name="line-27"></a><a name="composOp"></a><span class='hs-comment'>-- | @composOp == 'descend'@</span>
<a name="line-28"></a><span class='hs-definition'>composOp</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Uniplate</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</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-29"></a><span class='hs-definition'>composOp</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>descend</span>
<a name="line-30"></a>
<a name="line-31"></a>
<a name="line-32"></a><a name="composOpM"></a><span class='hs-comment'>-- | @composOpM == 'descendM'@</span>
<a name="line-33"></a><span class='hs-definition'>composOpM</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Uniplate</span> <span class='hs-varid'>a</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-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</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'>m</span> <span class='hs-varid'>a</span>
<a name="line-34"></a><span class='hs-definition'>composOpM</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>descendM</span>
<a name="line-35"></a>
<a name="line-36"></a>
<a name="line-37"></a><a name="composOpM_"></a><span class='hs-comment'>-- | @composOpM_ == 'composOpFold' (return ()) (>>)@</span>
<a name="line-38"></a><span class='hs-definition'>composOpM_</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Uniplate</span> <span class='hs-varid'>a</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-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</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'>m</span> <span class='hs-conid'>()</span>
<a name="line-39"></a><span class='hs-definition'>composOpM_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>composOpFold</span> <span class='hs-layout'>(</span><span class='hs-varid'>return</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varop'>>></span><span class='hs-layout'>)</span>
<a name="line-40"></a>
<a name="line-41"></a>
<a name="line-42"></a><a name="composOpMonoid"></a><span class='hs-comment'>-- | @composOpMonoid = 'composOpFold' mempty mappend@</span>
<a name="line-43"></a><span class='hs-definition'>composOpMonoid</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Uniplate</span> <span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>Monoid</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'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</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'>m</span>
<a name="line-44"></a><span class='hs-definition'>composOpMonoid</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>composOpFold</span> <span class='hs-varid'>mempty</span> <span class='hs-varid'>mappend</span>
<a name="line-45"></a>
<a name="line-46"></a>
<a name="line-47"></a><a name="composOpMPlus"></a><span class='hs-comment'>-- | @composOpMPlus = 'composOpFold' mzero mplus@</span>
<a name="line-48"></a><span class='hs-definition'>composOpMPlus</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Uniplate</span> <span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>MonadPlus</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'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>b</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'>m</span> <span class='hs-varid'>b</span>
<a name="line-49"></a><span class='hs-definition'>composOpMPlus</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>composOpFold</span> <span class='hs-varid'>mzero</span> <span class='hs-varid'>mplus</span>
<a name="line-50"></a>
<a name="line-51"></a>
<a name="line-52"></a><a name="composOpFold"></a><span class='hs-comment'>-- | Probably replace with 'universe', perhaps 'para'</span>
<a name="line-53"></a><span class='hs-definition'>composOpFold</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Uniplate</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>b</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-varid'>b</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-layout'>(</span><span class='hs-varid'>a</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'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span>
<a name="line-54"></a><span class='hs-definition'>composOpFold</span> <span class='hs-varid'>zero</span> <span class='hs-varid'>combine</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldr</span> <span class='hs-varid'>combine</span> <span class='hs-varid'>zero</span> <span class='hs-varop'>.</span> <span class='hs-varid'>map</span> <span class='hs-varid'>f</span> <span class='hs-varop'>.</span> <span class='hs-varid'>children</span>
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