204 lines
21 KiB
HTML
204 lines
21 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<head>
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<title>2/tgs</title>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="../inweb.css" rel="stylesheet" rev="stylesheet" type="text/css">
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</head>
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<body>
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<nav role="navigation">
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<h1><a href="../webs.html">Sources</a></h1>
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<ul>
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<li><a href="../inweb/index.html">inweb</a></li>
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</ul>
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<h2>Foundation</h2>
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<ul>
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<li><a href="../foundation-module/index.html">foundation-module</a></li>
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<li><a href="../foundation-test/index.html">foundation-test</a></li>
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</ul>
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</nav>
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<main role="main">
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<!--Weave of '2/ec' generated by 7-->
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<ul class="crumbs"><li><a href="../webs.html">Source</a></li><li><a href="index.html">inweb</a></li><li><a href="index.html#2">Chapter 2: Parsing a Web</a></li><li><b>Enumerated Constants</b></li></ul><p class="purpose">To define sequentially numbered values for families of constants.</p>
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<p class="inwebparagraph"><a id="SP1"></a><b>§1. </b>The idea here is that each enumeration set is a sequence of named constants
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with a given postfix: for example, <code class="display"><span class="extract">HARRY_ST</span></code>, <code class="display"><span class="extract">NEVILLE_ST</span></code>, <code class="display"><span class="extract">ANGELINA_ST</span></code>
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form the <code class="display"><span class="extract">*_ST</span></code> set. By definition, the postfix part is the portion of the
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name following the final underscore, so in this case <code class="display"><span class="extract">ST</span></code>.
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</p>
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<p class="inwebparagraph">Each set of constants begins at a given value (typically 0) and then
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increments sequentially in definition order.
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</p>
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<pre class="display">
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<span class="reserved">typedef</span><span class="plain"> </span><span class="reserved">struct</span><span class="plain"> </span><span class="reserved">enumeration_set</span><span class="plain"> {</span>
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<span class="reserved">struct</span><span class="plain"> </span><span class="reserved">text_stream</span><span class="plain"> *</span><span class="identifier">postfix</span><span class="plain">;</span>
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<span class="reserved">struct</span><span class="plain"> </span><span class="reserved">text_stream</span><span class="plain"> *</span><span class="identifier">stub</span><span class="plain">;</span>
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<span class="reserved">int</span><span class="plain"> </span><span class="identifier">first_value</span><span class="plain">;</span>
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<span class="reserved">int</span><span class="plain"> </span><span class="identifier">next_free_value</span><span class="plain">;</span>
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<span class="reserved">struct</span><span class="plain"> </span><span class="reserved">source_line</span><span class="plain"> *</span><span class="identifier">last_observed_at</span><span class="plain">;</span>
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<span class="constant">MEMORY_MANAGEMENT</span>
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<span class="plain">} </span><span class="reserved">enumeration_set</span><span class="plain">;</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">The structure enumeration_set is private to this section.</p>
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<p class="inwebparagraph"><a id="SP2"></a><b>§2. </b>There won't be enough sets to make a hash table worth the overhead, so
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compare all against all:
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</p>
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<pre class="display">
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<span class="reserved">enumeration_set</span><span class="plain"> *</span><span class="functiontext">Enumerations::find</span><span class="plain">(</span><span class="reserved">text_stream</span><span class="plain"> *</span><span class="identifier">post</span><span class="plain">) {</span>
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<span class="reserved">enumeration_set</span><span class="plain"> *</span><span class="identifier">es</span><span class="plain"> = </span><span class="identifier">NULL</span><span class="plain">;</span>
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<span class="identifier">LOOP_OVER</span><span class="plain">(</span><span class="identifier">es</span><span class="plain">, </span><span class="reserved">enumeration_set</span><span class="plain">)</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="functiontext">Str::eq</span><span class="plain">(</span><span class="identifier">post</span><span class="plain">, </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>postfix</span><span class="plain">))</span>
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<span class="reserved">return</span><span class="plain"> </span><span class="identifier">es</span><span class="plain">;</span>
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<span class="reserved">return</span><span class="plain"> </span><span class="identifier">NULL</span><span class="plain">;</span>
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<span class="plain">}</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">The function Enumerations::find is used in <a href="#SP3">§3</a>.</p>
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<p class="inwebparagraph"><a id="SP3"></a><b>§3. </b>The following is called when an enumeration is found. If <code class="display"><span class="extract">from</span></code> has a
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sensible value, this is the start of a new enumeration set; otherwise it's
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a further constant in what ought to be an existing set.
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</p>
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<pre class="display">
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<span class="reserved">void</span><span class="plain"> </span><span class="functiontext">Enumerations::define</span><span class="plain">(</span><span class="constant">OUTPUT_STREAM</span><span class="plain">, </span><span class="reserved">text_stream</span><span class="plain"> *</span><span class="identifier">symbol</span><span class="plain">,</span>
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<span class="reserved">text_stream</span><span class="plain"> *</span><span class="identifier">from</span><span class="plain">, </span><span class="reserved">source_line</span><span class="plain"> *</span><span class="identifier">L</span><span class="plain">) {</span>
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<span class="identifier">TEMPORARY_TEXT</span><span class="plain">(</span><span class="identifier">pf</span><span class="plain">);</span>
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<<span class="cwebmacro">Find the postfix in this symbol name</span> <span class="cwebmacronumber">3.1</span>><span class="plain">;</span>
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<span class="reserved">enumeration_set</span><span class="plain"> *</span><span class="identifier">es</span><span class="plain"> = </span><span class="functiontext">Enumerations::find</span><span class="plain">(</span><span class="identifier">pf</span><span class="plain">);</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">from</span><span class="plain"> == </span><span class="identifier">NULL</span><span class="plain">) </span><<span class="cwebmacro">Continue existing set</span> <span class="cwebmacronumber">3.2</span>>
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<span class="reserved">else</span><span class="plain"> </span><<span class="cwebmacro">Begin new set</span> <span class="cwebmacronumber">3.3</span>><span class="plain">;</span>
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<span class="identifier">DISCARD_TEXT</span><span class="plain">(</span><span class="identifier">pf</span><span class="plain">);</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">es</span><span class="plain">) </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>last_observed_at</span><span class="plain"> = </span><span class="identifier">L</span><span class="plain">;</span>
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<span class="plain">}</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">The function Enumerations::define is used in 2/tp (<a href="2-tp.html#SP1_1_6_5_1_7">§1.1.6.5.1.7</a>).</p>
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<p class="inwebparagraph"><a id="SP3_1"></a><b>§3.1. </b>So for instance <code class="display"><span class="extract">HARRY_ST</span></code> to <code class="display"><span class="extract">ST</span></code>:
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</p>
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<p class="macrodefinition"><code class="display">
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<<span class="cwebmacrodefn">Find the postfix in this symbol name</span> <span class="cwebmacronumber">3.1</span>> =
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</code></p>
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<pre class="displaydefn">
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<span class="reserved">match_results</span><span class="plain"> </span><span class="identifier">mr</span><span class="plain"> = </span><span class="functiontext">Regexp::create_mr</span><span class="plain">();</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="functiontext">Regexp::match</span><span class="plain">(&</span><span class="identifier">mr</span><span class="plain">, </span><span class="identifier">symbol</span><span class="plain">, </span><span class="identifier">L</span><span class="string">"%c*_(%C+?)"</span><span class="plain">)) </span><span class="functiontext">Str::copy</span><span class="plain">(</span><span class="identifier">pf</span><span class="plain">, </span><span class="identifier">mr</span><span class="element">.exp</span><span class="plain">[0]);</span>
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<span class="reserved">else</span><span class="plain"> {</span>
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<span class="functiontext">Main::error_in_web</span><span class="plain">(</span><span class="identifier">I</span><span class="string">"enumeration constants must belong to a _FAMILY"</span><span class="plain">, </span><span class="identifier">L</span><span class="plain">);</span>
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<span class="identifier">WRITE_TO</span><span class="plain">(</span><span class="identifier">pf</span><span class="plain">, </span><span class="string">"BOGUS"</span><span class="plain">);</span>
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<span class="plain">}</span>
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<span class="functiontext">Regexp::dispose_of</span><span class="plain">(&</span><span class="identifier">mr</span><span class="plain">);</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">This code is used in <a href="#SP3">§3</a>.</p>
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<p class="inwebparagraph"><a id="SP3_2"></a><b>§3.2. </b><code class="display">
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<<span class="cwebmacrodefn">Continue existing set</span> <span class="cwebmacronumber">3.2</span>> =
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</code></p>
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<pre class="displaydefn">
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">es</span><span class="plain">) {</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">es</span><span class="plain">-</span><span class="element">>stub</span><span class="plain">) </span><span class="identifier">WRITE</span><span class="plain">(</span><span class="string">"(%S+"</span><span class="plain">, </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>stub</span><span class="plain">);</span>
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<span class="identifier">WRITE</span><span class="plain">(</span><span class="string">"%d"</span><span class="plain">, </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>next_free_value</span><span class="plain">++);</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">es</span><span class="plain">-</span><span class="element">>stub</span><span class="plain">) </span><span class="identifier">WRITE</span><span class="plain">(</span><span class="string">")"</span><span class="plain">);</span>
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<span class="plain">} </span><span class="reserved">else</span><span class="plain"> </span><span class="functiontext">Main::error_in_web</span><span class="plain">(</span><span class="identifier">I</span><span class="string">"this enumeration _FAMILY is unknown"</span><span class="plain">, </span><span class="identifier">L</span><span class="plain">);</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">This code is used in <a href="#SP3">§3</a>.</p>
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<p class="inwebparagraph"><a id="SP3_3"></a><b>§3.3. </b><code class="display">
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<<span class="cwebmacrodefn">Begin new set</span> <span class="cwebmacronumber">3.3</span>> =
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</code></p>
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<pre class="displaydefn">
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">es</span><span class="plain">) </span><span class="functiontext">Main::error_in_web</span><span class="plain">(</span><span class="identifier">I</span><span class="string">"this enumeration _FAMILY already exists"</span><span class="plain">, </span><span class="identifier">L</span><span class="plain">);</span>
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<span class="reserved">else</span><span class="plain"> {</span>
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<span class="identifier">es</span><span class="plain"> = </span><span class="identifier">CREATE</span><span class="plain">(</span><span class="reserved">enumeration_set</span><span class="plain">);</span>
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<span class="identifier">es</span><span class="plain">-</span><span class="element">>postfix</span><span class="plain"> = </span><span class="functiontext">Str::duplicate</span><span class="plain">(</span><span class="identifier">pf</span><span class="plain">);</span>
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<span class="identifier">es</span><span class="plain">-</span><span class="element">>stub</span><span class="plain"> = </span><span class="identifier">NULL</span><span class="plain">;</span>
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<span class="reserved">if</span><span class="plain"> ((</span><span class="functiontext">Str::len</span><span class="plain">(</span><span class="identifier">from</span><span class="plain">) < 8) &&</span>
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<span class="plain">((</span><span class="functiontext">Regexp::match</span><span class="plain">(</span><span class="identifier">NULL</span><span class="plain">, </span><span class="identifier">from</span><span class="plain">, </span><span class="identifier">L</span><span class="string">"%d+"</span><span class="plain">)) ||</span>
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<span class="plain">(</span><span class="functiontext">Regexp::match</span><span class="plain">(</span><span class="identifier">NULL</span><span class="plain">, </span><span class="identifier">from</span><span class="plain">, </span><span class="identifier">L</span><span class="string">"-%d+"</span><span class="plain">)))) {</span>
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<span class="identifier">es</span><span class="plain">-</span><span class="element">>first_value</span><span class="plain"> = </span><span class="functiontext">Str::atoi</span><span class="plain">(</span><span class="identifier">from</span><span class="plain">, 0);</span>
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<span class="identifier">es</span><span class="plain">-</span><span class="element">>next_free_value</span><span class="plain"> = </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>first_value</span><span class="plain"> + 1;</span>
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<span class="plain">} </span><span class="reserved">else</span><span class="plain"> {</span>
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<span class="identifier">es</span><span class="plain">-</span><span class="element">>stub</span><span class="plain"> = </span><span class="functiontext">Str::duplicate</span><span class="plain">(</span><span class="identifier">from</span><span class="plain">);</span>
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<span class="identifier">es</span><span class="plain">-</span><span class="element">>first_value</span><span class="plain"> = 0;</span>
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<span class="identifier">es</span><span class="plain">-</span><span class="element">>next_free_value</span><span class="plain"> = 1;</span>
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<span class="plain">}</span>
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<span class="plain">}</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">es</span><span class="plain">-</span><span class="element">>stub</span><span class="plain">) </span><span class="identifier">WRITE</span><span class="plain">(</span><span class="string">"(%S+"</span><span class="plain">, </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>stub</span><span class="plain">);</span>
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<span class="identifier">WRITE</span><span class="plain">(</span><span class="string">"%d"</span><span class="plain">, </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>first_value</span><span class="plain">);</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">es</span><span class="plain">-</span><span class="element">>stub</span><span class="plain">) </span><span class="identifier">WRITE</span><span class="plain">(</span><span class="string">")"</span><span class="plain">);</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">This code is used in <a href="#SP3">§3</a>.</p>
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<p class="inwebparagraph"><a id="SP4"></a><b>§4. </b>For each set, a further constant is defined to give the range; for example,
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we would have <code class="display"><span class="extract">NO_DEFINED_ST_VALUES</span></code> set to 3. This is notionally placed in
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the code at the last line on which an <code class="display"><span class="extract">*_ST</span></code> value was defined.
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</p>
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<pre class="display">
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<span class="reserved">void</span><span class="plain"> </span><span class="functiontext">Enumerations::define_extents</span><span class="plain">(</span><span class="constant">OUTPUT_STREAM</span><span class="plain">, </span><span class="reserved">tangle_target</span><span class="plain"> *</span><span class="identifier">target</span><span class="plain">, </span><span class="reserved">programming_language</span><span class="plain"> *</span><span class="identifier">lang</span><span class="plain">) {</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">lang</span><span class="plain">-</span><span class="element">>supports_enumerations</span><span class="plain">) {</span>
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<span class="reserved">enumeration_set</span><span class="plain"> *</span><span class="identifier">es</span><span class="plain">;</span>
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<span class="identifier">LOOP_OVER</span><span class="plain">(</span><span class="identifier">es</span><span class="plain">, </span><span class="reserved">enumeration_set</span><span class="plain">) {</span>
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<span class="identifier">TEMPORARY_TEXT</span><span class="plain">(</span><span class="identifier">symbol</span><span class="plain">);</span>
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<span class="identifier">TEMPORARY_TEXT</span><span class="plain">(</span><span class="identifier">value</span><span class="plain">);</span>
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<span class="identifier">WRITE_TO</span><span class="plain">(</span><span class="identifier">symbol</span><span class="plain">, </span><span class="string">"NO_DEFINED_%S_VALUES"</span><span class="plain">, </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>postfix</span><span class="plain">);</span>
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<span class="identifier">WRITE_TO</span><span class="plain">(</span><span class="identifier">value</span><span class="plain">, </span><span class="string">"%d"</span><span class="plain">, </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>next_free_value</span><span class="plain"> - </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>first_value</span><span class="plain">);</span>
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<span class="functiontext">Languages::start_definition</span><span class="plain">(</span><span class="identifier">OUT</span><span class="plain">, </span><span class="identifier">lang</span><span class="plain">, </span><span class="identifier">symbol</span><span class="plain">, </span><span class="identifier">value</span><span class="plain">,</span>
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<span class="identifier">es</span><span class="plain">-</span><span class="element">>last_observed_at</span><span class="plain">-</span><span class="element">>owning_section</span><span class="plain">, </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>last_observed_at</span><span class="plain">);</span>
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<span class="functiontext">Languages::end_definition</span><span class="plain">(</span><span class="identifier">OUT</span><span class="plain">, </span><span class="identifier">lang</span><span class="plain">,</span>
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<span class="identifier">es</span><span class="plain">-</span><span class="element">>last_observed_at</span><span class="plain">-</span><span class="element">>owning_section</span><span class="plain">, </span><span class="identifier">es</span><span class="plain">-</span><span class="element">>last_observed_at</span><span class="plain">);</span>
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<span class="identifier">DISCARD_TEXT</span><span class="plain">(</span><span class="identifier">symbol</span><span class="plain">);</span>
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<span class="identifier">DISCARD_TEXT</span><span class="plain">(</span><span class="identifier">value</span><span class="plain">);</span>
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<span class="plain">}</span>
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<span class="plain">}</span>
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<span class="plain">}</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">The function Enumerations::define_extents is used in 3/tt (<a href="3-tt.html#SP1_1_1">§1.1.1</a>).</p>
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