<!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>src/Darcs/Patch/ReadMonads.hs</title> <link type='text/css' rel='stylesheet' href='hscolour.css' /> </head> <body> <pre><a name="line-1"></a> <a name="line-2"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Darcs</span><span class='hs-varop'>.</span><span class='hs-conid'>Patch</span><span class='hs-varop'>.</span><span class='hs-conid'>ReadMonads</span> <span class='hs-layout'>(</span><span class='hs-conid'>ParserM</span><span class='hs-layout'>,</span> <span class='hs-varid'>work</span><span class='hs-layout'>,</span> <span class='hs-varid'>maybe_work</span><span class='hs-layout'>,</span> <span class='hs-varid'>alter_input</span><span class='hs-layout'>,</span> <a name="line-3"></a> <span class='hs-varid'>parse_strictly</span><span class='hs-layout'>,</span> <span class='hs-varid'>parse_lazily</span><span class='hs-layout'>,</span> <a name="line-4"></a> <span class='hs-varid'>peek_input</span><span class='hs-layout'>,</span> <a name="line-5"></a> <span class='hs-varid'>lex_char</span><span class='hs-layout'>,</span> <span class='hs-varid'>lex_string</span><span class='hs-layout'>,</span> <span class='hs-varid'>lex_strings</span><span class='hs-layout'>,</span> <span class='hs-varid'>lex_eof</span><span class='hs-layout'>,</span> <a name="line-6"></a> <span class='hs-varid'>my_lex</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span> <a name="line-7"></a> <a name="line-8"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>ByteStringUtils</span> <span class='hs-layout'>(</span> <span class='hs-varid'>dropSpace</span><span class='hs-layout'>,</span> <span class='hs-varid'>breakSpace</span> <span class='hs-layout'>)</span> <a name="line-9"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>B</span> <span class='hs-layout'>(</span><span class='hs-varid'>null</span><span class='hs-layout'>,</span> <span class='hs-varid'>empty</span><span class='hs-layout'>,</span> <span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span> <a name="line-10"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-varop'>.</span><span class='hs-conid'>Char8</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>BC</span> <span class='hs-layout'>(</span><span class='hs-varid'>unpack</span><span class='hs-layout'>,</span> <span class='hs-varid'>pack</span><span class='hs-layout'>)</span> <a name="line-11"></a> <a name="line-12"></a><a name="lex_char"></a><span class='hs-definition'>lex_char</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ParserM</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Char</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span> <a name="line-13"></a><span class='hs-definition'>lex_char</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lex_string</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>c</span><span class='hs-keyglyph'>]</span> <a name="line-14"></a> <a name="line-15"></a><a name="lex_string"></a><span class='hs-definition'>lex_string</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ParserM</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>String</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span> <a name="line-16"></a><span class='hs-definition'>lex_string</span> <span class='hs-varid'>str</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>work</span> <a name="line-17"></a> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>my_lex</span> <span class='hs-varid'>s</span> <span class='hs-keyword'>of</span> <a name="line-18"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>xs</span><span class='hs-layout'>,</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>xs</span> <span class='hs-varop'>==</span> <span class='hs-conid'>BC</span><span class='hs-varop'>.</span><span class='hs-varid'>pack</span> <span class='hs-varid'>str</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>()</span><span class='hs-layout'>,</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span> <a name="line-19"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span> <a name="line-20"></a> <a name="line-21"></a><a name="lex_eof"></a><span class='hs-definition'>lex_eof</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ParserM</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span> <a name="line-22"></a><span class='hs-definition'>lex_eof</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>work</span> <a name="line-23"></a> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>if</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>null</span> <span class='hs-layout'>(</span><span class='hs-varid'>dropSpace</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <a name="line-24"></a> <span class='hs-keyword'>then</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>()</span><span class='hs-layout'>,</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>empty</span><span class='hs-layout'>)</span> <a name="line-25"></a> <span class='hs-keyword'>else</span> <span class='hs-conid'>Nothing</span> <a name="line-26"></a> <a name="line-27"></a><a name="lex_strings"></a><span class='hs-definition'>lex_strings</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ParserM</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>String</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>String</span> <a name="line-28"></a><span class='hs-definition'>lex_strings</span> <span class='hs-varid'>str</span> <span class='hs-keyglyph'>=</span> <a name="line-29"></a> <span class='hs-varid'>work</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <a name="line-30"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>my_lex</span> <span class='hs-varid'>s</span> <span class='hs-keyword'>of</span> <a name="line-31"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>xs</span><span class='hs-layout'>,</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>xs'</span> <span class='hs-varop'>`elem`</span> <span class='hs-varid'>str</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>xs'</span><span class='hs-layout'>,</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span> <a name="line-32"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>xs'</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>BC</span><span class='hs-varop'>.</span><span class='hs-varid'>unpack</span> <span class='hs-varid'>xs</span> <a name="line-33"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span> <a name="line-34"></a> <a name="line-35"></a><a name="my_lex"></a><span class='hs-definition'>my_lex</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>,</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span> <a name="line-36"></a><span class='hs-definition'>my_lex</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>let</span> <span class='hs-varid'>s'</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>dropSpace</span> <span class='hs-varid'>s</span> <a name="line-37"></a> <span class='hs-keyword'>in</span> <span class='hs-keyword'>if</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>null</span> <span class='hs-varid'>s'</span> <a name="line-38"></a> <span class='hs-keyword'>then</span> <span class='hs-conid'>Nothing</span> <a name="line-39"></a> <span class='hs-keyword'>else</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-varid'>breakSpace</span> <span class='hs-varid'>s'</span> <a name="line-40"></a> <a name="line-41"></a><a name="alter_input"></a><span class='hs-definition'>alter_input</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ParserM</span> <span class='hs-varid'>m</span> <a name="line-42"></a> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span> <a name="line-43"></a><span class='hs-definition'>alter_input</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>work</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>()</span><span class='hs-layout'>,</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-44"></a> <a name="line-45"></a><a name="ParserM"></a><span class='hs-keyword'>class</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ParserM</span> <span class='hs-varid'>m</span> <span class='hs-keyword'>where</span> <a name="line-46"></a> <span class='hs-varid'>work</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</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-47"></a> <span class='hs-varid'>maybe_work</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>Maybe</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <a name="line-48"></a> <span class='hs-varid'>peek_input</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>m</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <a name="line-49"></a> <a name="line-50"></a><a name="parse_strictly"></a><span class='hs-comment'>----- Strict Monad -----</span> <a name="line-51"></a><span class='hs-definition'>parse_strictly</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>SM</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span> <a name="line-52"></a><span class='hs-definition'>parse_strictly</span> <span class='hs-layout'>(</span><span class='hs-conid'>SM</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span> <a name="line-53"></a> <a name="line-54"></a><a name="SM"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>SM</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SM</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-55"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-conid'>SM</span> <span class='hs-keyword'>where</span> <a name="line-56"></a> <span class='hs-conid'>SM</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'>SM</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>m</span> <span class='hs-varid'>s</span> <span class='hs-keyword'>of</span> <a name="line-57"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span> <a name="line-58"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>s'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <a name="line-59"></a> <span class='hs-keyword'>case</span> <span class='hs-varid'>k</span> <span class='hs-varid'>x</span> <span class='hs-keyword'>of</span> <a name="line-60"></a> <span class='hs-conid'>SM</span> <span class='hs-varid'>y</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>y</span> <span class='hs-varid'>s'</span> <a name="line-61"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SM</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-62"></a> <span class='hs-varid'>fail</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SM</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span><span class='hs-layout'>)</span> <a name="line-63"></a> <a name="line-64"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ParserM</span> <span class='hs-conid'>SM</span> <span class='hs-keyword'>where</span> <a name="line-65"></a> <span class='hs-varid'>work</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SM</span> <span class='hs-varid'>f</span> <a name="line-66"></a> <span class='hs-varid'>maybe_work</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SM</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span> <span class='hs-keyword'>of</span> <a name="line-67"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>,</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-layout'>(</span><span class='hs-conid'>Just</span> <span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>s'</span><span class='hs-layout'>)</span> <a name="line-68"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>Nothing</span><span class='hs-layout'>,</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <a name="line-69"></a> <span class='hs-varid'>peek_input</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SM</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>s</span><span class='hs-layout'>,</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <a name="line-70"></a> <a name="line-71"></a><a name="parse_lazily"></a><span class='hs-comment'>----- Lazy Monad -----</span> <a name="line-72"></a><span class='hs-definition'>parse_lazily</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>LM</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span> <a name="line-73"></a><span class='hs-definition'>parse_lazily</span> <span class='hs-layout'>(</span><span class='hs-conid'>LM</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span> <a name="line-74"></a> <a name="line-75"></a><a name="LM"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>LM</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>LM</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-76"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Monad</span> <span class='hs-conid'>LM</span> <span class='hs-keyword'>where</span> <a name="line-77"></a> <span class='hs-conid'>LM</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'>LM</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>let</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>s'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>m</span> <span class='hs-varid'>s</span> <a name="line-78"></a> <span class='hs-conid'>LM</span> <span class='hs-varid'>y</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>k</span> <span class='hs-varid'>x</span> <a name="line-79"></a> <span class='hs-keyword'>in</span> <span class='hs-varid'>y</span> <span class='hs-varid'>s'</span> <a name="line-80"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>LM</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span><span class='hs-varid'>s</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <a name="line-81"></a> <span class='hs-varid'>fail</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>error</span> <span class='hs-varid'>s</span> <a name="line-82"></a> <a name="line-83"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ParserM</span> <span class='hs-conid'>LM</span> <span class='hs-keyword'>where</span> <a name="line-84"></a> <span class='hs-varid'>work</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>LM</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span> <span class='hs-keyword'>of</span> <a name="line-85"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>error</span> <span class='hs-str'>"parser error"</span> <a name="line-86"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>x</span> <a name="line-87"></a> <span class='hs-varid'>maybe_work</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>LM</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span> <span class='hs-keyword'>of</span> <a name="line-88"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Nothing</span><span class='hs-layout'>,</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <a name="line-89"></a> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>s'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Just</span> <span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>s'</span><span class='hs-layout'>)</span> <a name="line-90"></a> <span class='hs-varid'>peek_input</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>LM</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>s</span><span class='hs-layout'>,</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <a name="line-91"></a> </pre></body> </html>
