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  34   <h1>Source code for joy.parser</h1><div class="highlight"><pre>
  35 <span></span><span class="c1"># -*- coding: utf-8 -*-</span>
  36 <span class="c1">#</span>
  37 <span class="c1">#    Copyright © 2014, 2015, 2016, 2017 Simon Forman</span>
  38 <span class="c1">#</span>
  39 <span class="c1">#    This file is part of Thun.</span>
  40 <span class="c1">#</span>
  41 <span class="c1">#    Thun is free software: you can redistribute it and/or modify</span>
  42 <span class="c1">#    it under the terms of the GNU General Public License as published by</span>
  43 <span class="c1">#    the Free Software Foundation, either version 3 of the License, or</span>
  44 <span class="c1">#    (at your option) any later version.</span>
  45 <span class="c1">#</span>
  46 <span class="c1">#    Thun is distributed in the hope that it will be useful,</span>
  47 <span class="c1">#    but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
  48 <span class="c1">#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the</span>
  49 <span class="c1">#    GNU General Public License for more details.</span>
  50 <span class="c1">#</span>
  51 <span class="c1">#    You should have received a copy of the GNU General Public License</span>
  52 <span class="c1">#    along with Thun.  If not see &lt;http://www.gnu.org/licenses/&gt;.</span>
  53 <span class="c1">#</span>
  54 <span class="sd">&#39;&#39;&#39;</span>
  55 <span class="sd">This module exports a single function for converting text to a joy</span>
  56 <span class="sd">expression as well as a single Symbol class and a single Exception type.</span>
  57
  58 <span class="sd">The Symbol string class is used by the interpreter to recognize literals</span>
  59 <span class="sd">by the fact that they are not Symbol objects.</span>
  60
  61 <span class="sd">A crude grammar::</span>
  62
  63 <span class="sd">    joy = term*</span>
  64 <span class="sd">    term = int | float | string | &#39;[&#39; joy &#39;]&#39; | symbol</span>
  65
  66 <span class="sd">A Joy expression is a sequence of zero or more terms.  A term is a</span>
  67 <span class="sd">literal value (integer, float, string, or Joy expression) or a function</span>
  68 <span class="sd">symbol.  Function symbols are unquoted strings and cannot contain square</span>
  69 <span class="sd">brackets.   Terms must be separated by blanks, which can be omitted</span>
  70 <span class="sd">around square brackets.</span>
  71
  72 <span class="sd">&#39;&#39;&#39;</span>
  73 <span class="kn">from</span> <span class="nn">re</span> <span class="kn">import</span> <span class="n">Scanner</span>
  74 <span class="kn">from</span> <span class="nn">.utils.stack</span> <span class="kn">import</span> <span class="n">list_to_stack</span>
  75
  76
  77 <span class="c1">#TODO: explain the details of float lits and strings.</span>
  78 <span class="n">FLOAT</span> <span class="o">=</span> <span class="sa">r</span><span class="s1">&#39;-?\d+\.\d*&#39;</span>
  79 <span class="n">INT</span> <span class="o">=</span> <span class="sa">r</span><span class="s1">&#39;-?\d+&#39;</span>
  80 <span class="n">SYMBOL</span> <span class="o">=</span> <span class="sa">r</span><span class="s1">&#39;[•\w!@$%^&amp;*()_+&lt;&gt;?|\/;:`~,.=-]+&#39;</span>
  81 <span class="n">BRACKETS</span> <span class="o">=</span> <span class="sa">r</span><span class="s1">&#39;\[|\]&#39;</span>
  82 <span class="n">STRING_DOUBLE_QUOTED</span> <span class="o">=</span> <span class="sa">r</span><span class="s1">&#39;&quot;(?:[^&quot;</span><span class="se">\\</span><span class="s1">]|</span><span class="se">\\</span><span class="s1">.)*&quot;&#39;</span>
  83 <span class="n">STRING_SINGLE_QUOTED</span> <span class="o">=</span> <span class="sa">r</span><span class="s2">&quot;&#39;(?:[^&#39;</span><span class="se">\\</span><span class="s2">]|</span><span class="se">\\</span><span class="s2">.)*&#39;&quot;</span>
  84 <span class="n">BLANKS</span> <span class="o">=</span> <span class="sa">r</span><span class="s1">&#39;\s+&#39;</span>
  85
  86
  87 <div class="viewcode-block" id="Symbol"><a class="viewcode-back" href="../../parser.html#joy.parser.Symbol">[docs]</a><span class="k">class</span> <span class="nc">Symbol</span><span class="p">(</span><span class="nb">str</span><span class="p">):</span>
  88         <span class="sd">&#39;&#39;&#39;A string class that represents Joy function names.&#39;&#39;&#39;</span>
  89         <span class="fm">__repr__</span> <span class="o">=</span> <span class="nb">str</span><span class="o">.</span><span class="fm">__str__</span></div>
  90
  91
  92 <div class="viewcode-block" id="text_to_expression"><a class="viewcode-back" href="../../parser.html#joy.parser.text_to_expression">[docs]</a><span class="k">def</span> <span class="nf">text_to_expression</span><span class="p">(</span><span class="n">text</span><span class="p">):</span>
  93         <span class="sd">&#39;&#39;&#39;Convert a string to a Joy expression.</span>
  94
  95 <span class="sd">       When supplied with a string this function returns a Python datastructure</span>
  96 <span class="sd">       that represents the Joy datastructure described by the text expression.</span>
  97 <span class="sd">       Any unbalanced square brackets will raise a ParseError.</span>
  98
  99 <span class="sd">       :param str text: Text to convert.</span>
 100 <span class="sd">       :rtype: stack</span>
 101 <span class="sd">       :raises ParseError: if the parse fails.</span>
 102 <span class="sd">       &#39;&#39;&#39;</span>
 103         <span class="k">return</span> <span class="n">_parse</span><span class="p">(</span><span class="n">_tokenize</span><span class="p">(</span><span class="n">text</span><span class="p">))</span></div>
 104
 105
 106 <div class="viewcode-block" id="ParseError"><a class="viewcode-back" href="../../parser.html#joy.parser.ParseError">[docs]</a><span class="k">class</span> <span class="nc">ParseError</span><span class="p">(</span><span class="ne">ValueError</span><span class="p">):</span>
 107         <span class="sd">&#39;&#39;&#39;Raised when there is a error while parsing text.&#39;&#39;&#39;</span></div>
 108
 109
 110 <span class="k">def</span> <span class="nf">_tokenize</span><span class="p">(</span><span class="n">text</span><span class="p">):</span>
 111         <span class="sd">&#39;&#39;&#39;Convert a text into a stream of tokens.</span>
 112
 113 <span class="sd">       Converts function names to Symbols.</span>
 114
 115 <span class="sd">       Raise ParseError (with some of the failing text) if the scan fails.</span>
 116 <span class="sd">       &#39;&#39;&#39;</span>
 117         <span class="n">tokens</span><span class="p">,</span> <span class="n">rest</span> <span class="o">=</span> <span class="n">_scanner</span><span class="o">.</span><span class="n">scan</span><span class="p">(</span><span class="n">text</span><span class="p">)</span>
 118         <span class="k">if</span> <span class="n">rest</span><span class="p">:</span>
 119                 <span class="k">raise</span> <span class="n">ParseError</span><span class="p">(</span>
 120                         <span class="s1">&#39;Scan failed at position </span><span class="si">%i</span><span class="s1">, </span><span class="si">%r</span><span class="s1">&#39;</span>
 121                         <span class="o">%</span> <span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">text</span><span class="p">)</span> <span class="o">-</span> <span class="nb">len</span><span class="p">(</span><span class="n">rest</span><span class="p">),</span> <span class="n">rest</span><span class="p">[:</span><span class="mi">10</span><span class="p">])</span>
 122                         <span class="p">)</span>
 123         <span class="k">return</span> <span class="n">tokens</span>
 124
 125
 126 <span class="k">def</span> <span class="nf">_parse</span><span class="p">(</span><span class="n">tokens</span><span class="p">):</span>
 127         <span class="sd">&#39;&#39;&#39;</span>
 128 <span class="sd">       Return a stack/list expression of the tokens.</span>
 129 <span class="sd">       &#39;&#39;&#39;</span>
 130         <span class="n">frame</span> <span class="o">=</span> <span class="p">[]</span>
 131         <span class="n">stack</span> <span class="o">=</span> <span class="p">[]</span>
 132         <span class="k">for</span> <span class="n">tok</span> <span class="ow">in</span> <span class="n">tokens</span><span class="p">:</span>
 133                 <span class="k">if</span> <span class="n">tok</span> <span class="o">==</span> <span class="s1">&#39;[&#39;</span><span class="p">:</span>
 134                         <span class="n">stack</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">frame</span><span class="p">)</span>
 135                         <span class="n">frame</span> <span class="o">=</span> <span class="p">[]</span>
 136                         <span class="n">stack</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">frame</span><span class="p">)</span>
 137                 <span class="k">elif</span> <span class="n">tok</span> <span class="o">==</span> <span class="s1">&#39;]&#39;</span><span class="p">:</span>
 138                         <span class="k">try</span><span class="p">:</span>
 139                                 <span class="n">frame</span> <span class="o">=</span> <span class="n">stack</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span>
 140                         <span class="k">except</span> <span class="ne">IndexError</span><span class="p">:</span>
 141                                 <span class="k">raise</span> <span class="n">ParseError</span><span class="p">(</span><span class="s1">&#39;Extra closing bracket.&#39;</span><span class="p">)</span>
 142                         <span class="n">frame</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="o">=</span> <span class="n">list_to_stack</span><span class="p">(</span><span class="n">frame</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">])</span>
 143                 <span class="k">else</span><span class="p">:</span>
 144                         <span class="n">frame</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">tok</span><span class="p">)</span>
 145         <span class="k">if</span> <span class="n">stack</span><span class="p">:</span>
 146                 <span class="k">raise</span> <span class="n">ParseError</span><span class="p">(</span><span class="s1">&#39;Unclosed bracket.&#39;</span><span class="p">)</span>
 147         <span class="k">return</span> <span class="n">list_to_stack</span><span class="p">(</span><span class="n">frame</span><span class="p">)</span>
 148
 149
 150 <span class="n">_scanner</span> <span class="o">=</span> <span class="n">Scanner</span><span class="p">([</span>
 151         <span class="p">(</span><span class="n">FLOAT</span><span class="p">,</span> <span class="k">lambda</span> <span class="n">_</span><span class="p">,</span> <span class="n">token</span><span class="p">:</span> <span class="nb">float</span><span class="p">(</span><span class="n">token</span><span class="p">)),</span>
 152         <span class="p">(</span><span class="n">INT</span><span class="p">,</span> <span class="k">lambda</span> <span class="n">_</span><span class="p">,</span> <span class="n">token</span><span class="p">:</span> <span class="nb">int</span><span class="p">(</span><span class="n">token</span><span class="p">)),</span>
 153         <span class="p">(</span><span class="n">SYMBOL</span><span class="p">,</span> <span class="k">lambda</span> <span class="n">_</span><span class="p">,</span> <span class="n">token</span><span class="p">:</span> <span class="n">Symbol</span><span class="p">(</span><span class="n">token</span><span class="p">)),</span>
 154         <span class="p">(</span><span class="n">BRACKETS</span><span class="p">,</span> <span class="k">lambda</span> <span class="n">_</span><span class="p">,</span> <span class="n">token</span><span class="p">:</span> <span class="n">token</span><span class="p">),</span>
 155         <span class="p">(</span><span class="n">STRING_DOUBLE_QUOTED</span><span class="p">,</span> <span class="k">lambda</span> <span class="n">_</span><span class="p">,</span> <span class="n">token</span><span class="p">:</span> <span class="n">token</span><span class="p">[</span><span class="mi">1</span><span class="p">:</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="s1">&#39;</span><span class="se">\\</span><span class="s1">&quot;&#39;</span><span class="p">,</span> <span class="s1">&#39;&quot;&#39;</span><span class="p">)),</span>
 156         <span class="p">(</span><span class="n">STRING_SINGLE_QUOTED</span><span class="p">,</span> <span class="k">lambda</span> <span class="n">_</span><span class="p">,</span> <span class="n">token</span><span class="p">:</span> <span class="n">token</span><span class="p">[</span><span class="mi">1</span><span class="p">:</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="s2">&quot;</span><span class="se">\\</span><span class="s2">&#39;&quot;</span><span class="p">,</span> <span class="s2">&quot;&#39;&quot;</span><span class="p">)),</span>
 157         <span class="p">(</span><span class="n">BLANKS</span><span class="p">,</span> <span class="kc">None</span><span class="p">),</span>
 158         <span class="p">])</span>
 159 </pre></div>
 160
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 167 <h1 class="logo"><a href="../../index.html">Thun</a></h1>
 168
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 172
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 174
 175
 176 <h3>Navigation</h3>
 177 <ul>
 178 <li class="toctree-l1"><a class="reference internal" href="../../notebooks/Intro.html">Thun: Joy in Python</a></li>
 179 <li class="toctree-l1"><a class="reference internal" href="../../joy.html">Joy Interpreter</a></li>
 180 <li class="toctree-l1"><a class="reference internal" href="../../stack.html">Stack or Quote or Sequence or List…</a></li>
 181 <li class="toctree-l1"><a class="reference internal" href="../../parser.html">Parsing Text into Joy Expressions</a></li>
 182 <li class="toctree-l1"><a class="reference internal" href="../../pretty.html">Tracing Joy Execution</a></li>
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 185 <li class="toctree-l1"><a class="reference internal" href="../../types.html">Type Inference of Joy Expressions</a></li>
 186 <li class="toctree-l1"><a class="reference internal" href="../../notebooks/index.html">Essays about Programming in Joy</a></li>
 187 </ul>
 188
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 190 <h3>Related Topics</h3>
 191 <ul>
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