GF-for-Python-programmers/Types.html at master · daherb/GF-for-Python-programmers · GitHub

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<div id="content">
<div id="table-of-contents">
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#org24057cb">1. Types</a>
<ul>
<li>
<ul>
<li><a href="#org7d77866">1.0.1. Basic types</a></li>
<li><a href="#org6dccf80">1.0.2. Enumeration types</a></li>
<li><a href="#orgca9122b">1.0.3. Compound types</a></li>
<li><a href="#orge383ec0">1.0.4. Functions</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
</div>
<div id="outline-container-org24057cb" class="outline-2">
<h2 id="org24057cb"><span class="section-number-2">1</span> Types</h2>
<div class="outline-text-2" id="text-1">
<ul class="org-ul">
<li>GF is statically typed:
You cannot say something like
&#x2026;
a = 3 ;
a = "Foo" ;
&#x2026;</li>
<li>GF makes a distinction into abstract syntax/concrete syntax as well as resource modules</li>
</ul>
</div>

<div id="outline-container-org7d77866" class="outline-4">
<h4 id="org7d77866"><span class="section-number-4">1.0.1</span> Basic types</h4>
<div class="outline-text-4" id="text-1-0-1">
<ul class="org-ul">
<li>GF also support some basic types
<ul class="org-ul">
<li>Python has strings (called `str`). GF has strings (called `Str`).</li>
<li>Python has integers (called `int`). GF has integers (called `Int`).</li>
<li>Python has floating-point numbers (called `float`). GF's are called `Float`.</li>
</ul></li>
<li>These types can be used in resource modules and concrete syntax files</li>
<li>Strings vs. String tuples
<ul class="org-ul">
<li>Substrings can be concatenated with <b>+</b></li>
<li>Sentences in GF are kind of lists of strings, <b>++</b> concatenates lists of strings</li>
</ul></li>
<li><p>
Example:
</p>
<div class="org-src-container">
<pre class="src src-gf"><span style="color: #a020f0;">resource</span> <span style="color: #228b22;">SimpleTypes</span> <span style="color: #a0522d;">=</span> <span style="color: #a020f0;">open</span> Predef,Prelude <span style="color: #a020f0;">in</span> {
  <span style="color: #a020f0;">oper</span>
    s <span style="color: #a0522d;">:</span> Str <span style="color: #a0522d;">=</span> <span style="color: #8b2252;">"foo"</span> <span style="color: #a0522d;">+</span> <span style="color: #8b2252;">"bar"</span> ;
    st <span style="color: #a0522d;">:</span> Str <span style="color: #a0522d;">=</span> <span style="color: #8b2252;">"foo"</span> <span style="color: #a0522d;">++</span> <span style="color: #8b2252;">"bar"</span>;
    i <span style="color: #a0522d;">:</span> Predef<span style="color: #a0522d;">.</span>Int <span style="color: #a0522d;">=</span> 42;
    f <span style="color: #a0522d;">:</span> Predef<span style="color: #a0522d;">.</span>Float <span style="color: #a0522d;">=</span> 23<span style="color: #a0522d;">.</span>5;
    b <span style="color: #a0522d;">:</span> Bool <span style="color: #a0522d;">=</span> False ;
}
</pre>
</div></li>
</ul>
</div>
</div>

<div id="outline-container-org6dccf80" class="outline-4">
<h4 id="org6dccf80"><span class="section-number-4">1.0.2</span> Enumeration types</h4>
<div class="outline-text-4" id="text-1-0-2">
<ul class="org-ul">
<li>The only kind of enumeration types in GF are the so-called <b>param</b> types</li>

<li><p>
Example:
</p>
<div class="org-src-container">
<pre class="src src-gf"><span style="color: #a020f0;">resource</span> <span style="color: #228b22;">Param</span> <span style="color: #a0522d;">=</span> {
  <span style="color: #a020f0;">param</span>
    Gender <span style="color: #a0522d;">=</span> F <span style="color: #a0522d;">|</span> M ;
    Number <span style="color: #a0522d;">=</span> Sg <span style="color: #a0522d;">|</span> Pl ;
    Case <span style="color: #a0522d;">=</span> Nom <span style="color: #a0522d;">|</span> Gen <span style="color: #a0522d;">|</span> Acc <span style="color: #a0522d;">|</span> Dat ;
}
</pre>
</div></li>
</ul>
</div>
</div>

<div id="outline-container-orgca9122b" class="outline-4">
<h4 id="orgca9122b"><span class="section-number-4">1.0.3</span> Compound types</h4>
<div class="outline-text-4" id="text-1-0-3">
<ul class="org-ul">
<li>GF has three kinds of compound types, tables, records and tuples, Python has dictionaries, tuples and lists</li>
<li>GF does not really have lists</li>
<li>Keys in tables usually are *param*s and keys in records are literal identifier</li>

<li><p>
Example:
</p>
<div class="org-src-container">
<pre class="src src-gf"><span style="color: #a020f0;">resource</span> <span style="color: #228b22;">Compound</span> <span style="color: #a0522d;">=</span> Param <span style="color: #a0522d;">**</span> {
  <span style="color: #b22222;">-- </span><span style="color: #b22222;">Content of Param.gf</span>
  <span style="color: #b22222;">-- </span><span style="color: #b22222;">param</span>
  <span style="color: #b22222;">--   </span><span style="color: #b22222;">Gender = F | M ;</span>
  <span style="color: #b22222;">--   </span><span style="color: #b22222;">Number = Sg | Pl ;</span>
  <span style="color: #b22222;">--   </span><span style="color: #b22222;">Case = Nom | Gen | Acc | Dat ;</span>
  <span style="color: #a020f0;">param</span>
    Person <span style="color: #a0522d;">=</span> P1 <span style="color: #a0522d;">|</span> P2 <span style="color: #a0522d;">|</span> P3 ;
  <span style="color: #a020f0;">oper</span>
    sleep <span style="color: #a0522d;">:</span> Number <span style="color: #a0522d;">=&gt;</span> Person <span style="color: #a0522d;">=&gt;</span> Str <span style="color: #a0522d;">=</span> <span style="color: #b22222;">-- </span><span style="color: #b22222;">Declaration</span>
      <span style="color: #a020f0;">table</span> { <span style="color: #b22222;">-- </span><span style="color: #b22222;">Definition</span>
        Sg <span style="color: #a0522d;">=&gt;</span> <span style="color: #a020f0;">table</span> {
          P1 <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"sleep"</span> ;
          P2 <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"sleep"</span> ;
          P3 <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"sleeps"</span>
          } ;
        Pl <span style="color: #a0522d;">=&gt;</span> <span style="color: #a020f0;">table</span> {
          P1 <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"sleep"</span> ;
          P2 <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"sleep"</span> ;
          P3 <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"sleep"</span>
          }
      };
    theSg <span style="color: #a0522d;">:</span> { s <span style="color: #a0522d;">:</span> Str ; n <span style="color: #a0522d;">:</span> Number } <span style="color: #a0522d;">=</span> <span style="color: #b22222;">-- </span><span style="color: #b22222;">Declaration</span>
      { s <span style="color: #a0522d;">=</span> <span style="color: #8b2252;">"the"</span> ; n <span style="color: #a0522d;">=</span> Sg } ; <span style="color: #b22222;">-- </span><span style="color: #b22222;">Definition</span>

    man <span style="color: #a0522d;">:</span> { s <span style="color: #a0522d;">:</span> Number <span style="color: #a0522d;">=&gt;</span> Case <span style="color: #a0522d;">=&gt;</span> Str ; g <span style="color: #a0522d;">:</span> Gender } <span style="color: #b22222;">-- </span><span style="color: #b22222;">Declaration</span>
      <span style="color: #a0522d;">=</span> { s <span style="color: #a0522d;">=</span> <span style="color: #a020f0;">table</span> {
            Sg <span style="color: #a0522d;">=&gt;</span> <span style="color: #a020f0;">table</span> {
              Nom <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"man"</span> ;
              Gen <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"man's"</span> ;
              Dat <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"man"</span> ;
              Acc <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"man"</span>
              } ;
            Pl <span style="color: #a0522d;">=&gt;</span> <span style="color: #a020f0;">table</span> {
              Gen <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"men's"</span> ;
              _ <span style="color: #a0522d;">=&gt;</span> <span style="color: #8b2252;">"men"</span> }
            } ;
          g <span style="color: #a0522d;">=</span> M
      } ;
}
</pre>
</div></li>

<li>To select values from tables the <b>!</b> operator is used, to select from records the <b>.</b> operator</li>
<li>Tuples are special cases of records</li>
</ul>
</div>
</div>

<div id="outline-container-orge383ec0" class="outline-4">
<h4 id="orge383ec0"><span class="section-number-4">1.0.4</span> Functions</h4>
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<li>GF supports both regular functions and anonymous functions</li>

<li><p>
Example:
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<pre class="src src-gf"><span style="color: #a020f0;">resource</span> <span style="color: #228b22;">Functions</span> <span style="color: #a0522d;">=</span> <span style="color: #a020f0;">open</span> Prelude,Predef <span style="color: #a020f0;">in</span> {
  <span style="color: #a020f0;">oper</span>
    succ <span style="color: #a0522d;">:</span> Int <span style="color: #a0522d;">-&gt;</span> Int; <span style="color: #b22222;">-- </span><span style="color: #b22222;">Declaration</span>
    succ i <span style="color: #a0522d;">=</span> plus i 1 ; <span style="color: #b22222;">-- </span><span style="color: #b22222;">Definition</span>
    succ2 <span style="color: #a0522d;">:</span> Int <span style="color: #a0522d;">-&gt;</span> Int <span style="color: #a0522d;">=</span> <span style="color: #b22222;">-- </span><span style="color: #b22222;">Declaration</span>
      <span style="color: #a0522d;">\</span>i <span style="color: #a0522d;">-&gt;</span> plus i 1; <span style="color: #b22222;">-- </span><span style="color: #b22222;">Definition</span>
}
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<div id="postamble" class="status">
<p class="author">Author: Herbert Lange</p>
<p class="date">Created: 2018-04-18 Wed 11:25</p>
<p class="validation"><a href="http://validator.w3.org/check?uri=referer">Validate</a></p>
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