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<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="../compiler.html">Inter Modules</a></li><li><a href="index.html">pipeline</a></li><li><a href="index.html#4">Chapter 4: Linking</a></li><li><b>Shorten Wiring Stage</b></li></ul></div>
<p class="purpose">To catch missing resources with suitable errors, to remove plugs and sockets as no longer necessary, and to shorten wiring as much as possible.</p>
<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>&#167;1. </b></p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">void</span><span class="plain-syntax"> </span><span class="function-syntax">ShortenWiringStage::create_pipeline_stage</span><button class="popup" onclick="togglePopup('usagePopup1')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup1">Usage of <span class="code-font"><span class="function-syntax">ShortenWiringStage::create_pipeline_stage</span></span>:<br/>Parsing Pipelines - <a href="2-pp.html#SP10">&#167;10</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">void</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><a href="2-pp.html#SP3" class="function-link"><span class="function-syntax">ParsingPipelines::new_stage</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">I</span><span class="string-syntax">"shorten-wiring"</span><span class="plain-syntax">,</span>
<span class="plain-syntax"> </span><a href="4-sws.html#SP2" class="function-link"><span class="function-syntax">ShortenWiringStage::run</span></a><span class="plain-syntax">, </span><span class="constant-syntax">NO_STAGE_ARG</span><span class="plain-syntax">, </span><span class="identifier-syntax">FALSE</span><span class="plain-syntax">);</span>
<span class="plain-syntax">}</span>
</pre>
<p class="commentary firstcommentary"><a id="SP2" class="paragraph-anchor"></a><b>&#167;2. </b>In practice, linking errors can occur when the source text refers to a function
which doesn't exist in any kit: if the user has mistyped <span class="extract"><span class="extract-syntax">ExmapleKitFunction</span></span>, say,
then the plug would never find a socket with a matching name. We want to catch
and report these errors efficiently, so we keep the bad names in both a dictionary
(for quick lookup) and a list (for reporting).
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">typedef</span><span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">plug_inspection_state</span><span class="plain-syntax"> {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="identifier-syntax">dictionary</span><span class="plain-syntax"> *</span><span class="identifier-syntax">bad_plugs</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="identifier-syntax">linked_list</span><span class="plain-syntax"> *</span><span class="identifier-syntax">bad_plug_names</span><span class="plain-syntax">; </span><span class="comment-syntax"> of </span><span class="extract"><span class="extract-syntax">text_stream</span></span>
<span class="plain-syntax">} </span><span class="reserved-syntax">plug_inspection_state</span><span class="plain-syntax">;</span>
<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">ShortenWiringStage::run</span><button class="popup" onclick="togglePopup('usagePopup2')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup2">Usage of <span class="code-font"><span class="function-syntax">ShortenWiringStage::run</span></span>:<br/><a href="4-sws.html#SP1">&#167;1</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">pipeline_step</span><span class="plain-syntax"> *</span><span class="identifier-syntax">step</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">inter_tree</span><span class="plain-syntax"> *</span><span class="identifier-syntax">I</span><span class="plain-syntax"> = </span><span class="identifier-syntax">step</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">ephemera</span><span class="plain-syntax">.</span><span class="element-syntax">tree</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="4-sws.html#SP2_1" class="named-paragraph-link"><span class="named-paragraph">Shorten the wiring and report loose plugs</span><span class="named-paragraph-number">2.1</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">inter_package</span><span class="plain-syntax"> *</span><span class="identifier-syntax">connectors</span><span class="plain-syntax"> = </span><span class="identifier-syntax">LargeScale::connectors_package_if_it_exists</span><span class="plain-syntax">(</span><span class="identifier-syntax">I</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">connectors</span><span class="plain-syntax">) </span><span class="named-paragraph-container code-font"><a href="4-sws.html#SP2_2" class="named-paragraph-link"><span class="named-paragraph">Remove the now unnecessary plugs and sockets</span><span class="named-paragraph-number">2.2</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">TRUE</span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
</pre>
<ul class="endnotetexts"><li>The structure plug_inspection_state is private to this section.</li></ul>
<p class="commentary firstcommentary"><a id="SP2_1" class="paragraph-anchor"></a><b>&#167;2.1. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Shorten the wiring and report loose plugs</span><span class="named-paragraph-number">2.1</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="reserved-syntax">plug_inspection_state</span><span class="plain-syntax"> </span><span class="identifier-syntax">state</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">state</span><span class="plain-syntax">.</span><span class="identifier-syntax">bad_plugs</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Dictionaries::new</span><span class="plain-syntax">(16, </span><span class="identifier-syntax">FALSE</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">state</span><span class="plain-syntax">.</span><span class="identifier-syntax">bad_plug_names</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NEW_LINKED_LIST</span><span class="plain-syntax">(</span><span class="identifier-syntax">text_stream</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">InterTree::traverse</span><span class="plain-syntax">(</span><span class="identifier-syntax">I</span><span class="plain-syntax">, </span><a href="4-sws.html#SP3" class="function-link"><span class="function-syntax">ShortenWiringStage::visitor</span></a><span class="plain-syntax">, &amp;</span><span class="identifier-syntax">state</span><span class="plain-syntax">, </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">, </span><span class="identifier-syntax">PACKAGE_IST</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">LinkedLists::len</span><span class="plain-syntax">(</span><span class="identifier-syntax">state</span><span class="plain-syntax">.</span><span class="element-syntax">bad_plug_names</span><span class="plain-syntax">) &gt; </span><span class="constant-syntax">0</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">TEMPORARY_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">NS</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">N</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">LOOP_OVER_LINKED_LIST</span><span class="plain-syntax">(</span><span class="identifier-syntax">N</span><span class="plain-syntax">, </span><span class="identifier-syntax">text_stream</span><span class="plain-syntax">, </span><span class="identifier-syntax">state</span><span class="plain-syntax">.</span><span class="element-syntax">bad_plug_names</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">Str::len</span><span class="plain-syntax">(</span><span class="identifier-syntax">NS</span><span class="plain-syntax">) &gt; </span><span class="constant-syntax">0</span><span class="plain-syntax">) </span><span class="identifier-syntax">WRITE_TO</span><span class="plain-syntax">(</span><span class="identifier-syntax">NS</span><span class="plain-syntax">, </span><span class="string-syntax">", "</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">WRITE_TO</span><span class="plain-syntax">(</span><span class="identifier-syntax">NS</span><span class="plain-syntax">, </span><span class="string-syntax">"%S"</span><span class="plain-syntax">, </span><span class="identifier-syntax">N</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> </span><a href="2-pe.html#SP2" class="function-link"><span class="function-syntax">PipelineErrors::error_with</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">step</span><span class="plain-syntax">,</span>
<span class="plain-syntax"> </span><span class="string-syntax">"unable to find definitions for the following name(s): %S"</span><span class="plain-syntax">, </span><span class="identifier-syntax">NS</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">DISCARD_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">NS</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">FALSE</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> }</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="4-sws.html#SP2">&#167;2</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP3" class="paragraph-anchor"></a><b>&#167;3. </b>Note that it is not necessarily an error to have a loose plug, that is, a plug
which does not connect to any socket. It is only an error if a symbol is trying
to connect to this plug. So we make a traverse of the tree to look for such symbols.
</p>
<p class="commentary">Note that we also take the opportunity to simplify chains of equations down to just
the minimum. For example, if we have <span class="extract"><span class="extract-syntax">S1 -&gt; S2 -&gt; plug -&gt; socket -&gt; T1 -&gt; T2 -&gt; T3</span></span>,
we simplify just to <span class="extract"><span class="extract-syntax">S1 -&gt; T3</span></span>.
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">void</span><span class="plain-syntax"> </span><span class="function-syntax">ShortenWiringStage::visitor</span><button class="popup" onclick="togglePopup('usagePopup3')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup3">Usage of <span class="code-font"><span class="function-syntax">ShortenWiringStage::visitor</span></span>:<br/><a href="4-sws.html#SP2_1">&#167;2.1</a></span></button><span class="plain-syntax">(</span><span class="identifier-syntax">inter_tree</span><span class="plain-syntax"> *</span><span class="identifier-syntax">I</span><span class="plain-syntax">, </span><span class="identifier-syntax">inter_tree_node</span><span class="plain-syntax"> *</span><span class="identifier-syntax">P</span><span class="plain-syntax">, </span><span class="reserved-syntax">void</span><span class="plain-syntax"> *</span><span class="identifier-syntax">v_state</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">plug_inspection_state</span><span class="plain-syntax"> *</span><span class="identifier-syntax">state</span><span class="plain-syntax"> = (</span><span class="reserved-syntax">plug_inspection_state</span><span class="plain-syntax"> *) </span><span class="identifier-syntax">v_state</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">inter_package</span><span class="plain-syntax"> *</span><span class="identifier-syntax">Q</span><span class="plain-syntax"> = </span><span class="identifier-syntax">InterPackage::at_this_head</span><span class="plain-syntax">(</span><span class="identifier-syntax">P</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">inter_symbols_table</span><span class="plain-syntax"> *</span><span class="identifier-syntax">ST</span><span class="plain-syntax"> = </span><span class="identifier-syntax">InterPackage::scope</span><span class="plain-syntax">(</span><span class="identifier-syntax">Q</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">LOOP_OVER_SYMBOLS_TABLE</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">, </span><span class="identifier-syntax">ST</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">inter_symbol</span><span class="plain-syntax"> *</span><span class="identifier-syntax">E</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Wiring::cable_end</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">S</span><span class="plain-syntax"> != </span><span class="identifier-syntax">E</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">Wiring::shorten_wiring</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">Wiring::is_loose_plug</span><span class="plain-syntax">(</span><span class="identifier-syntax">E</span><span class="plain-syntax">))</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="4-sws.html#SP3_1" class="named-paragraph-link"><span class="named-paragraph">This is an error, because a loose plug has been used</span><span class="named-paragraph-number">3.1</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax">}</span>
</pre>
<p class="commentary firstcommentary"><a id="SP3_1" class="paragraph-anchor"></a><b>&#167;3.1. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">This is an error, because a loose plug has been used</span><span class="named-paragraph-number">3.1</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="identifier-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">N</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Wiring::name_sought_by_loose_plug</span><span class="plain-syntax">(</span><span class="identifier-syntax">E</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">Dictionaries::find</span><span class="plain-syntax">(</span><span class="identifier-syntax">state</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">bad_plugs</span><span class="plain-syntax">, </span><span class="identifier-syntax">N</span><span class="plain-syntax">) == </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">Dictionaries::create</span><span class="plain-syntax">(</span><span class="identifier-syntax">state</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">bad_plugs</span><span class="plain-syntax">, </span><span class="identifier-syntax">N</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">ADD_TO_LINKED_LIST</span><span class="plain-syntax">(</span><span class="identifier-syntax">N</span><span class="plain-syntax">, </span><span class="identifier-syntax">text_stream</span><span class="plain-syntax">, </span><span class="identifier-syntax">state</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">bad_plug_names</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> }</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="4-sws.html#SP3">&#167;3</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP2_2" class="paragraph-anchor"></a><b>&#167;2.2. </b>At this point there will be plugs with no incoming connections, but which
are each wired to sockets. Removing the plugs first then leaves the sockets
with no incoming connections either, and so the sockets can go too.
</p>
<p class="commentary">The result should be a completely empty <span class="extract"><span class="extract-syntax">connectors</span></span> module.
</p>
<p class="commentary"><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Remove the now unnecessary plugs and sockets</span><span class="named-paragraph-number">2.2</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="identifier-syntax">inter_symbols_table</span><span class="plain-syntax"> *</span><span class="identifier-syntax">ST</span><span class="plain-syntax"> = </span><span class="identifier-syntax">InterPackage::scope</span><span class="plain-syntax">(</span><span class="identifier-syntax">connectors</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="4-sws.html#SP2_2_1" class="named-paragraph-link"><span class="named-paragraph">Remove plugs with no incoming connections</span><span class="named-paragraph-number">2.2.1</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="4-sws.html#SP2_2_2" class="named-paragraph-link"><span class="named-paragraph">Remove sockets with no incoming connections</span><span class="named-paragraph-number">2.2.2</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="4-sws.html#SP2_2_3" class="named-paragraph-link"><span class="named-paragraph">Report any remaining symbols in this table as errors</span><span class="named-paragraph-number">2.2.3</span></a></span><span class="plain-syntax">;</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="4-sws.html#SP2">&#167;2</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP2_2_1" class="paragraph-anchor"></a><b>&#167;2.2.1. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Remove plugs with no incoming connections</span><span class="named-paragraph-number">2.2.1</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="identifier-syntax">LOOP_OVER_SYMBOLS_TABLE</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">, </span><span class="identifier-syntax">ST</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">InterSymbol::is_plug</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">)) &amp;&amp; (</span><span class="identifier-syntax">Wiring::has_no_incoming_connections</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">)))</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">InterSymbolsTable::remove_symbol</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> }</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="4-sws.html#SP2_2">&#167;2.2</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP2_2_2" class="paragraph-anchor"></a><b>&#167;2.2.2. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Remove sockets with no incoming connections</span><span class="named-paragraph-number">2.2.2</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="identifier-syntax">LOOP_OVER_SYMBOLS_TABLE</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">, </span><span class="identifier-syntax">ST</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">InterSymbol::is_socket</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">)) &amp;&amp; (</span><span class="identifier-syntax">Wiring::has_no_incoming_connections</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">)))</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">InterSymbolsTable::remove_symbol</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> }</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="4-sws.html#SP2_2">&#167;2.2</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP2_2_3" class="paragraph-anchor"></a><b>&#167;2.2.3. </b>This should never happen:
</p>
<p class="commentary"><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Report any remaining symbols in this table as errors</span><span class="named-paragraph-number">2.2.3</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">errors</span><span class="plain-syntax"> = </span><span class="constant-syntax">0</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">LOOP_OVER_SYMBOLS_TABLE</span><span class="plain-syntax">(</span><span class="identifier-syntax">S</span><span class="plain-syntax">, </span><span class="identifier-syntax">ST</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">LOG</span><span class="plain-syntax">(</span><span class="string-syntax">"Connector not deleted: %3\n"</span><span class="plain-syntax">, </span><span class="identifier-syntax">S</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">errors</span><span class="plain-syntax">++;</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">errors</span><span class="plain-syntax"> &gt; </span><span class="constant-syntax">0</span><span class="plain-syntax">) </span><span class="identifier-syntax">internal_error</span><span class="plain-syntax">(</span><span class="string-syntax">"plugs and sockets mismanaged"</span><span class="plain-syntax">);</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="4-sws.html#SP2_2">&#167;2.2</a>.</li></ul>
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