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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="../inform7n.html">Inform7</a></li><li><a href="index.html">runtime</a></li><li><a href="index.html#4">Chapter 4: Enclosed Resources</a></li><li><b>Relation Literals</b></li></ul></div>
<p class="purpose">In fact there is only one literal relation: the empty one, used as a default value.</p>
<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>&#167;1. </b>It seems odd to call it a literal, but this:
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="identifier-syntax">let</span><span class="plain-syntax"> </span><span class="identifier-syntax">Q</span><span class="plain-syntax"> </span><span class="identifier-syntax">be</span><span class="plain-syntax"> </span><span class="identifier-syntax">a</span><span class="plain-syntax"> </span><span class="identifier-syntax">relation</span><span class="plain-syntax"> </span><span class="identifier-syntax">of</span><span class="plain-syntax"> </span><span class="identifier-syntax">numbers</span><span class="plain-syntax">;</span>
</pre>
<p class="commentary">sets up <span class="extract"><span class="extract-syntax">Q</span></span> to be a new empty relation &mdash; one in which, as yet, no number is
related to any other.
</p>
<p class="commentary">The following function compiles an array ready to be <span class="extract"><span class="extract-syntax">Q</span></span>, with some initial
capacity in it to absorb relationships forged at runtime. This is the default
value of kinds using the "relation of K to U" constructor.
</p>
<p class="commentary">The runtime representation of temporary relations like this one is complex.
See <a href="5-rlt.html" class="internal">Relations</a> and <a href="../BasicInformKit/S-rlt2.html" class="internal">Relations (in BasicInformKit)</a>.
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="identifier-syntax">inter_name</span><span class="plain-syntax"> *</span><span class="function-syntax">RelationLiterals::default</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">RelationLiterals::default</span></span>:<br/>Default Values - <a href="2-dv.html#SP2_1">&#167;2.1</a></span></button><span class="plain-syntax">(</span><span class="identifier-syntax">kind</span><span class="plain-syntax"> *</span><span class="identifier-syntax">K</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">inter_name</span><span class="plain-syntax"> *</span><span class="identifier-syntax">small_block</span><span class="plain-syntax"> = </span><a href="4-enc.html#SP2" class="function-link"><span class="function-syntax">Enclosures::new_small_block_for_constant</span></a><span class="plain-syntax">();</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">packaging_state</span><span class="plain-syntax"> </span><span class="identifier-syntax">save</span><span class="plain-syntax"> = </span><a href="2-ea.html#SP2" class="function-link"><span class="function-syntax">EmitArrays::begin_unchecked</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">small_block</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><a href="2-th.html#SP6" class="function-link"><span class="function-syntax">TheHeap::emit_block_value_header</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">K</span><span class="plain-syntax">, </span><span class="identifier-syntax">FALSE</span><span class="plain-syntax">, </span><span class="constant-syntax">34</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::null_entry</span></a><span class="plain-syntax">();</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::null_entry</span></a><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">DVT</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">DVT</span><span class="plain-syntax">, </span><span class="string-syntax">"anonymous "</span><span class="plain-syntax">); </span><span class="identifier-syntax">Kinds::Textual::write</span><span class="plain-syntax">(</span><span class="identifier-syntax">DVT</span><span class="plain-syntax">, </span><span class="identifier-syntax">K</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::text_entry</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">DVT</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">DVT</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::iname_entry</span></a><span class="plain-syntax">(</span><a href="2-hrr.html#SP11" class="function-link"><span class="function-syntax">Hierarchy::find</span></a><span class="plain-syntax">(</span><span class="constant-syntax">TTF_SUM_HL</span><span class="plain-syntax">));</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::numeric_entry</span></a><span class="plain-syntax">(7);</span>
<span class="plain-syntax"> </span><a href="5-ki.html#SP6" class="function-link"><span class="function-syntax">RTKindIDs::strong_ID_array_entry</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">K</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">kind</span><span class="plain-syntax"> *</span><span class="identifier-syntax">EK</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Kinds::unary_construction_material</span><span class="plain-syntax">(</span><span class="identifier-syntax">K</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">Kinds::Behaviour::uses_block_values</span><span class="plain-syntax">(</span><span class="identifier-syntax">EK</span><span class="plain-syntax">))</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::iname_entry</span></a><span class="plain-syntax">(</span><a href="2-hrr.html#SP11" class="function-link"><span class="function-syntax">Hierarchy::find</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">HASHLISTRELATIONHANDLER_HL</span><span class="plain-syntax">));</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">else</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::iname_entry</span></a><span class="plain-syntax">(</span><a href="2-hrr.html#SP11" class="function-link"><span class="function-syntax">Hierarchy::find</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">DOUBLEHASHSETRELATIONHANDLER_HL</span><span class="plain-syntax">));</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::text_entry</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">I</span><span class="string-syntax">"an anonymous relation"</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::numeric_entry</span></a><span class="plain-syntax">(0);</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::numeric_entry</span></a><span class="plain-syntax">(0);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">i</span><span class="plain-syntax">=0; </span><span class="identifier-syntax">i</span><span class="plain-syntax">&lt;24; </span><span class="identifier-syntax">i</span><span class="plain-syntax">++) </span><a href="2-ea.html#SP4" class="function-link"><span class="function-syntax">EmitArrays::numeric_entry</span></a><span class="plain-syntax">(0);</span>
<span class="plain-syntax"> </span><a href="2-ea.html#SP5" class="function-link"><span class="function-syntax">EmitArrays::end</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">save</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">small_block</span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
</pre>
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