<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html> <head> <!-- Generated by HsColour, http://www.cs.york.ac.uk/fp/darcs/hscolour/ --> <title>Network/MPD/Commands/Query.hs</title> <link type='text/css' rel='stylesheet' href='hscolour.css' /> </head> <body> <pre><a name="line-1"></a><span class='hs-comment'>-- | Module : Network.MPD.Commands.Query</span> <a name="line-2"></a><span class='hs-comment'>-- Copyright : (c) Ben Sinclair 2005-2009, Joachim Fasting 2010</span> <a name="line-3"></a><span class='hs-comment'>-- License : LGPL (see LICENSE)</span> <a name="line-4"></a><span class='hs-comment'>-- Maintainer : Joachim Fasting <joachim.fasting@gmail.com></span> <a name="line-5"></a><span class='hs-comment'>-- Stability : alpha</span> <a name="line-6"></a><span class='hs-comment'>--</span> <a name="line-7"></a><span class='hs-comment'>-- Query interface.</span> <a name="line-8"></a> <a name="line-9"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Network</span><span class='hs-varop'>.</span><span class='hs-conid'>MPD</span><span class='hs-varop'>.</span><span class='hs-conid'>Commands</span><span class='hs-varop'>.</span><span class='hs-conid'>Query</span> <span class='hs-layout'>(</span><span class='hs-conid'>Query</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-varop'>=?</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-varop'><&></span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>anything</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span> <a name="line-10"></a> <a name="line-11"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Network</span><span class='hs-varop'>.</span><span class='hs-conid'>MPD</span><span class='hs-varop'>.</span><span class='hs-conid'>Commands</span><span class='hs-varop'>.</span><span class='hs-conid'>Arg</span> <a name="line-12"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Network</span><span class='hs-varop'>.</span><span class='hs-conid'>MPD</span><span class='hs-varop'>.</span><span class='hs-conid'>Commands</span><span class='hs-varop'>.</span><span class='hs-conid'>Types</span> <a name="line-13"></a> <a name="line-14"></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-15"></a> <a name="line-16"></a><a name="Query"></a><span class='hs-comment'>-- | An interface for creating MPD queries.</span> <a name="line-17"></a><a name="Query"></a><span class='hs-comment'>--</span> <a name="line-18"></a><a name="Query"></a><span class='hs-comment'>-- For example, to match any song where the value of artist is \"Foo\", we</span> <a name="line-19"></a><a name="Query"></a><span class='hs-comment'>-- use:</span> <a name="line-20"></a><a name="Query"></a><span class='hs-comment'>--</span> <a name="line-21"></a><a name="Query"></a><span class='hs-comment'>-- > Artist =? "Foo"</span> <a name="line-22"></a><a name="Query"></a><span class='hs-comment'>--</span> <a name="line-23"></a><a name="Query"></a><span class='hs-comment'>-- We can also compose queries, thus narrowing the search. For example, to</span> <a name="line-24"></a><a name="Query"></a><span class='hs-comment'>-- match any song where the value of artist is \"Foo\" and the value of album</span> <a name="line-25"></a><a name="Query"></a><span class='hs-comment'>-- is \"Bar\", we use:</span> <a name="line-26"></a><a name="Query"></a><span class='hs-comment'>--</span> <a name="line-27"></a><a name="Query"></a><span class='hs-comment'>-- > Artist =? "Foo" <&> Album =? "Bar"</span> <a name="line-28"></a><a name="Query"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Match</span><span class='hs-keyglyph'>]</span> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Show</span> <a name="line-29"></a> <a name="line-30"></a><a name="Match"></a><span class='hs-comment'>-- A single query clause, comprising a metadata key and a desired value.</span> <a name="line-31"></a><a name="Match"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Match</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Match</span> <span class='hs-conid'>Meta</span> <span class='hs-conid'>String</span> <a name="line-32"></a> <a name="line-33"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-conid'>Match</span> <span class='hs-keyword'>where</span> <a name="line-34"></a> <span class='hs-varid'>show</span> <span class='hs-layout'>(</span><span class='hs-conid'>Match</span> <span class='hs-varid'>meta</span> <span class='hs-varid'>query</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>show</span> <span class='hs-varid'>meta</span> <span class='hs-varop'>++</span> <span class='hs-str'>" \""</span> <span class='hs-varop'>++</span> <span class='hs-varid'>query</span> <span class='hs-varop'>++</span> <span class='hs-str'>"\""</span> <a name="line-35"></a> <span class='hs-varid'>showList</span> <span class='hs-varid'>xs</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unwords</span> <span class='hs-varop'>$</span> <span class='hs-varid'>map</span> <span class='hs-varid'>show</span> <span class='hs-varid'>xs</span> <a name="line-36"></a> <a name="line-37"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monoid</span> <span class='hs-conid'>Query</span> <span class='hs-keyword'>where</span> <a name="line-38"></a> <span class='hs-varid'>mempty</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Query</span> <span class='hs-conid'>[]</span> <a name="line-39"></a> <span class='hs-conid'>Query</span> <span class='hs-varid'>a</span> <span class='hs-varop'>`mappend`</span> <span class='hs-conid'>Query</span> <span class='hs-varid'>b</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Query</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-varop'>++</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <a name="line-40"></a> <a name="line-41"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>MPDArg</span> <span class='hs-conid'>Query</span> <span class='hs-keyword'>where</span> <a name="line-42"></a> <span class='hs-varid'>prep</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldl</span> <span class='hs-layout'>(</span><span class='hs-varop'><++></span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Args</span> <span class='hs-conid'>[]</span><span class='hs-layout'>)</span> <span class='hs-varop'>.</span> <span class='hs-varid'>f</span> <a name="line-43"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>Query</span> <span class='hs-varid'>ms</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>map</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>Match</span> <span class='hs-varid'>m</span> <span class='hs-varid'>q</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Args</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>show</span> <span class='hs-varid'>m</span><span class='hs-keyglyph'>]</span> <span class='hs-varop'><++></span> <span class='hs-varid'>q</span><span class='hs-layout'>)</span> <span class='hs-varid'>ms</span> <a name="line-44"></a> <a name="line-45"></a><a name="anything"></a><span class='hs-comment'>-- | An empty query. Matches anything.</span> <a name="line-46"></a><span class='hs-definition'>anything</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Query</span> <a name="line-47"></a><span class='hs-definition'>anything</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mempty</span> <a name="line-48"></a> <a name="line-49"></a><a name="=?"></a><span class='hs-comment'>-- | Create a query.</span> <a name="line-50"></a><span class='hs-layout'>(</span><span class='hs-varop'>=?</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Meta</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>String</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Query</span> <a name="line-51"></a><a name="m"></a><span class='hs-definition'>m</span> <span class='hs-varop'>=?</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Match</span> <span class='hs-varid'>m</span> <span class='hs-varid'>s</span><span class='hs-keyglyph'>]</span> <a name="line-52"></a> <a name="line-53"></a><span class='hs-comment'>-- | Combine queries.</span> <a name="line-54"></a><span class='hs-keyword'>infixr</span> <span class='hs-num'>6</span> <span class='hs-varop'><&></span> <a name="line-55"></a><a name="<&>"></a><span class='hs-layout'>(</span><span class='hs-varop'><&></span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Query</span> <a name="line-56"></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'>mappend</span> </pre></body> </html>
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