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  36   <section id="type-checking">
  37 <h1>Type Checking<a class="headerlink" href="#type-checking" title="Permalink to this headline">¶</a></h1>
  38 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>import logging, sys
  39
  40 logging.basicConfig(
  41   format=&#39;%(message)s&#39;,
  42   stream=sys.stdout,
  43   level=logging.INFO,
  44   )
  45 </pre></div>
  46 </div>
  47 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>from joy.utils.types import (
  48     doc_from_stack_effect,
  49     infer,
  50     reify,
  51     unify,
  52     FUNCTIONS,
  53     JoyTypeError,
  54 )
  55 </pre></div>
  56 </div>
  57 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>D = FUNCTIONS.copy()
  58 del D[&#39;product&#39;]
  59 globals().update(D)
  60 </pre></div>
  61 </div>
  62 <section id="an-example">
  63 <h2>An Example<a class="headerlink" href="#an-example" title="Permalink to this headline">¶</a></h2>
  64 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>fi, fo = infer(pop, swap, rolldown, rrest, ccons)[0]
  65 </pre></div>
  66 </div>
  67 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span>25 (--) ∘ pop swap rolldown rrest ccons
  68 28 (a1 --) ∘ swap rolldown rrest ccons
  69 31 (a3 a2 a1 -- a2 a3) ∘ rolldown rrest ccons
  70 34 (a4 a3 a2 a1 -- a2 a3 a4) ∘ rrest ccons
  71 37 ([a4 a5 ...1] a3 a2 a1 -- a2 a3 [...1]) ∘ ccons
  72 40 ([a4 a5 ...1] a3 a2 a1 -- [a2 a3 ...1]) ∘
  73 </pre></div>
  74 </div>
  75 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>print doc_from_stack_effect(fi, fo)
  76 </pre></div>
  77 </div>
  78 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">([</span><span class="n">a4</span> <span class="n">a5</span> <span class="o">...</span><span class="mi">1</span><span class="p">]</span> <span class="n">a3</span> <span class="n">a2</span> <span class="n">a1</span> <span class="o">--</span> <span class="p">[</span><span class="n">a2</span> <span class="n">a3</span> <span class="o">...</span><span class="mi">1</span><span class="p">])</span>
  79 </pre></div>
  80 </div>
  81 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>from joy.parser import text_to_expression
  82 from joy.utils.stack import stack_to_string
  83 </pre></div>
  84 </div>
  85 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>e = text_to_expression(&#39;0 1 2 [3 4]&#39;)  # reverse order
  86 print stack_to_string(e)
  87 </pre></div>
  88 </div>
  89 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">[</span><span class="mi">3</span> <span class="mi">4</span><span class="p">]</span> <span class="mi">2</span> <span class="mi">1</span> <span class="mi">0</span>
  90 </pre></div>
  91 </div>
  92 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>u = unify(e, fi)[0]
  93 u
  94 </pre></div>
  95 </div>
  96 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">{</span><span class="n">a1</span><span class="p">:</span> <span class="mi">0</span><span class="p">,</span> <span class="n">a2</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="n">a3</span><span class="p">:</span> <span class="mi">2</span><span class="p">,</span> <span class="n">a4</span><span class="p">:</span> <span class="mi">3</span><span class="p">,</span> <span class="n">a5</span><span class="p">:</span> <span class="mi">4</span><span class="p">,</span> <span class="n">s2</span><span class="p">:</span> <span class="p">(),</span> <span class="n">s1</span><span class="p">:</span> <span class="p">()}</span>
  97 </pre></div>
  98 </div>
  99 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>g = reify(u, (fi, fo))
 100 print doc_from_stack_effect(*g)
 101 </pre></div>
 102 </div>
 103 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="o">...</span> <span class="p">[</span><span class="mi">3</span> <span class="mi">4</span> <span class="p">]</span> <span class="mi">2</span> <span class="mi">1</span> <span class="mi">0</span> <span class="o">--</span> <span class="o">...</span> <span class="p">[</span><span class="mi">1</span> <span class="mi">2</span> <span class="p">])</span>
 104 </pre></div>
 105 </div>
 106 </section>
 107 <section id="unification-works-in-reverse">
 108 <h2>Unification Works “in Reverse”<a class="headerlink" href="#unification-works-in-reverse" title="Permalink to this headline">¶</a></h2>
 109 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>e = text_to_expression(&#39;[2 3]&#39;)
 110 </pre></div>
 111 </div>
 112 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>u = unify(e, fo)[0]  # output side, not input side
 113 u
 114 </pre></div>
 115 </div>
 116 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">{</span><span class="n">a2</span><span class="p">:</span> <span class="mi">2</span><span class="p">,</span> <span class="n">a3</span><span class="p">:</span> <span class="mi">3</span><span class="p">,</span> <span class="n">s2</span><span class="p">:</span> <span class="p">(),</span> <span class="n">s1</span><span class="p">:</span> <span class="p">()}</span>
 117 </pre></div>
 118 </div>
 119 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>g = reify(u, (fi, fo))
 120 print doc_from_stack_effect(*g)
 121 </pre></div>
 122 </div>
 123 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="o">...</span> <span class="p">[</span><span class="n">a4</span> <span class="n">a5</span> <span class="p">]</span> <span class="mi">3</span> <span class="mi">2</span> <span class="n">a1</span> <span class="o">--</span> <span class="o">...</span> <span class="p">[</span><span class="mi">2</span> <span class="mi">3</span> <span class="p">])</span>
 124 </pre></div>
 125 </div>
 126 </section>
 127 <section id="failing-a-check">
 128 <h2>Failing a Check<a class="headerlink" href="#failing-a-check" title="Permalink to this headline">¶</a></h2>
 129 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>fi, fo = infer(dup, mul)[0]
 130 </pre></div>
 131 </div>
 132 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span>25 (--) ∘ dup mul
 133 28 (a1 -- a1 a1) ∘ mul
 134 31 (f1 -- f2) ∘
 135 31 (i1 -- i2) ∘
 136 </pre></div>
 137 </div>
 138 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>e = text_to_expression(&#39;&quot;two&quot;&#39;)
 139 print stack_to_string(e)
 140 </pre></div>
 141 </div>
 142 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="s1">&#39;two&#39;</span>
 143 </pre></div>
 144 </div>
 145 <div class="highlight-ipython2 notranslate"><div class="highlight"><pre><span></span>try:
 146     unify(e, fi)
 147 except JoyTypeError, err:
 148     print err
 149 </pre></div>
 150 </div>
 151 <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">Cannot</span> <span class="n">unify</span> <span class="s1">&#39;two&#39;</span> <span class="ow">and</span> <span class="n">f1</span><span class="o">.</span>
 152 </pre></div>
 153 </div>
 154 </section>
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 173 <h3>Navigation</h3>
 174 <ul class="current">
 175 <li class="toctree-l1"><a class="reference internal" href="Intro.html">Thun: Joy in Python</a></li>
 176 <li class="toctree-l1"><a class="reference internal" href="../joy.html">Joy Interpreter</a></li>
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 193 <li class="toctree-l2"><a class="reference internal" href="Types.html">The Blissful Elegance of Typing Joy</a></li>
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 241 <span xmlns:dct="http://purl.org/dc/terms/" property="dct:title">Thun Documentation</span> by <a xmlns:cc="http://creativecommons.org/ns#" href="https://joypy.osdn.io/" property="cc:attributionName" rel="cc:attributionURL">Simon Forman</a> is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License</a>.<br />Based on a work at <a xmlns:dct="http://purl.org/dc/terms/" href="https://osdn.net/projects/joypy/" rel="dct:source">https://osdn.net/projects/joypy/</a>.
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