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<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="../inbuildn.html">Inbuild Modules</a></li><li><a href="index.html">supervisor</a></li><li><a href="index.html#6">Chapter 6: Inform Source Text</a></li><li><b>Virtual Machine Grammar</b></li></ul></div>
<p class="purpose">Grammar for parsing natural language descriptions of a virtual machine.</p>
<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>&#167;1. </b>This nonterminal corresponds to the Inbuild version number syntax in the
arch module: for example, it matches <span class="extract"><span class="extract-syntax">2.7.6</span></span> or <span class="extract"><span class="extract-syntax">3/990505</span></span>. A bit
awkwardly, because a semantic version number is stored as an actual <span class="extract"><span class="extract-syntax">struct</span></span>
rather than being created on the heap as an object: so we can't make the
return value of this nonterminal a pointer to that <span class="extract"><span class="extract-syntax">struct</span></span>, as that would be
out of scope when needed. Instead, we have to wrap it up in a holder object
to give it permanency.
</p>
<pre class="Preform-displayed-code all-displayed-code code-font">
<span class="Preform-function-syntax">&lt;version-number&gt;</span><span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">internal</span><span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">1</span><span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">{</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">TEMPORARY_TEXT</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">vtext</span><span class="Preform-plain-syntax">)</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">WRITE_TO</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">vtext</span><span class="Preform-plain-syntax">, </span><span class="Preform-string-syntax">"%W"</span><span class="Preform-plain-syntax">, </span><span class="Preform-identifier-syntax">W</span><span class="Preform-plain-syntax">);</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">semantic_version_number</span><span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">V</span><span class="Preform-plain-syntax"> = </span><span class="Preform-identifier-syntax">VersionNumbers::from_text</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">vtext</span><span class="Preform-plain-syntax">);</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">DISCARD_TEXT</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">vtext</span><span class="Preform-plain-syntax">)</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">if</span><span class="Preform-plain-syntax"> (</span><span class="Preform-identifier-syntax">VersionNumbers::is_null</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">V</span><span class="Preform-plain-syntax">) == </span><span class="Preform-identifier-syntax">FALSE</span><span class="Preform-plain-syntax">) {</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">semantic_version_number_holder</span><span class="Preform-plain-syntax"> *</span><span class="Preform-identifier-syntax">H</span><span class="Preform-plain-syntax"> = </span><span class="Preform-identifier-syntax">CREATE</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">semantic_version_number_holder</span><span class="Preform-plain-syntax">);</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">H</span><span class="Preform-plain-syntax">-&gt;</span><span class="Preform-identifier-syntax">version</span><span class="Preform-plain-syntax"> = </span><span class="Preform-identifier-syntax">V</span><span class="Preform-plain-syntax">;</span>
<span class="Preform-plain-syntax"> ==&gt; { -, </span><span class="Preform-identifier-syntax">H</span><span class="Preform-plain-syntax"> };</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">return</span><span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">TRUE</span><span class="Preform-plain-syntax">;</span>
<span class="Preform-plain-syntax"> }</span>
<span class="Preform-plain-syntax"> ==&gt; { </span><span class="Preform-identifier-syntax">fail</span><span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">nonterminal</span><span class="Preform-plain-syntax"> };</span>
<span class="Preform-plain-syntax">}</span>
</pre>
<ul class="endnotetexts"><li>This is <a href="../words-module/4-ap.html" class="internal">Preform grammar</a>, not regular C code.</li></ul>
<p class="commentary firstcommentary"><a id="SP2" class="paragraph-anchor"></a><b>&#167;2. </b>The following nonterminal matches any valid description of a virtual machine.
</p>
<pre class="Preform-displayed-code all-displayed-code code-font">
<span class="Preform-function-syntax">&lt;virtual-machine&gt;</span><span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">internal</span><span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">{</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">TEMPORARY_TEXT</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">vtext</span><span class="Preform-plain-syntax">)</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">WRITE_TO</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">vtext</span><span class="Preform-plain-syntax">, </span><span class="Preform-string-syntax">"%W"</span><span class="Preform-plain-syntax">, </span><span class="Preform-identifier-syntax">W</span><span class="Preform-plain-syntax">);</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">compatibility_specification</span><span class="Preform-plain-syntax"> *</span><span class="Preform-identifier-syntax">C</span><span class="Preform-plain-syntax"> = </span><span class="Preform-identifier-syntax">Compatibility::from_text</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">vtext</span><span class="Preform-plain-syntax">);</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">DISCARD_TEXT</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">vtext</span><span class="Preform-plain-syntax">)</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">if</span><span class="Preform-plain-syntax"> (</span><span class="Preform-identifier-syntax">C</span><span class="Preform-plain-syntax">) {</span>
<span class="Preform-plain-syntax"> ==&gt; { -, </span><span class="Preform-identifier-syntax">C</span><span class="Preform-plain-syntax"> };</span>
<span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">return</span><span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">TRUE</span><span class="Preform-plain-syntax">;</span>
<span class="Preform-plain-syntax"> }</span>
<span class="Preform-plain-syntax"> ==&gt; { </span><span class="Preform-identifier-syntax">fail</span><span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">nonterminal</span><span class="Preform-plain-syntax"> };</span>
<span class="Preform-plain-syntax">}</span>
</pre>
<ul class="endnotetexts"><li>This is <a href="../words-module/4-ap.html" class="internal">Preform grammar</a>, not regular C code.</li></ul>
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