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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">assertions</a></li><li><a href="index.html#8">Chapter 8: Predicates</a></li><li><b>The Equality Relation Revisited</b></li></ul></div>
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<p class="purpose">To define how equality behaves in the Inform language.</p>
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<ul class="toc"><li><a href="8-terr.html#SP1">§1. Additional details</a></li><li><a href="8-terr.html#SP2">§2. Typechecking</a></li><li><a href="8-terr.html#SP4">§4. Assertion</a></li><li><a href="8-terr.html#SP5">§5. Compilation</a></li></ul><hr class="tocbar">
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<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>§1. Additional details. </b></p>
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<pre class="displayed-code all-displayed-code code-font">
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<span class="reserved-syntax">void</span><span class="plain-syntax"> </span><span class="function-syntax">EqualityDetails::start</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">EqualityDetails::start</span></span>:<br/>Assertions Module - <a href="1-am.html#SP2">§2</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">void</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">METHOD_ADD</span><span class="plain-syntax">(</span><span class="identifier-syntax">equality_bp_family</span><span class="plain-syntax">, </span><span class="identifier-syntax">TYPECHECK_BPF_MTID</span><span class="plain-syntax">, </span><a href="8-terr.html#SP2" class="function-link"><span class="function-syntax">EqualityDetails::typecheck</span></a><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">METHOD_ADD</span><span class="plain-syntax">(</span><span class="identifier-syntax">equality_bp_family</span><span class="plain-syntax">, </span><span class="identifier-syntax">ASSERT_BPF_MTID</span><span class="plain-syntax">, </span><a href="8-terr.html#SP4" class="function-link"><span class="function-syntax">EqualityDetails::assert</span></a><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">METHOD_ADD</span><span class="plain-syntax">(</span><span class="identifier-syntax">equality_bp_family</span><span class="plain-syntax">, </span><span class="identifier-syntax">SCHEMA_BPF_MTID</span><span class="plain-syntax">, </span><a href="8-terr.html#SP5" class="function-link"><span class="function-syntax">EqualityDetails::schema</span></a><span class="plain-syntax">);</span>
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<span class="plain-syntax">}</span>
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</pre>
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<p class="commentary firstcommentary"><a id="SP2" class="paragraph-anchor"></a><b>§2. Typechecking. </b>This is a very polymorphic relation, in that it can accept terms of almost
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any kind.
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</p>
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<pre class="displayed-code all-displayed-code code-font">
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<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">EqualityDetails::typecheck</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">EqualityDetails::typecheck</span></span>:<br/><a href="8-terr.html#SP1">§1</a></span></button><span class="plain-syntax">(</span><span class="identifier-syntax">bp_family</span><span class="plain-syntax"> *</span><span class="identifier-syntax">self</span><span class="plain-syntax">, </span><span class="identifier-syntax">binary_predicate</span><span class="plain-syntax"> *</span><span class="identifier-syntax">bp</span><span class="plain-syntax">,</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">kind</span><span class="plain-syntax"> **</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">, </span><span class="identifier-syntax">kind</span><span class="plain-syntax"> **</span><span class="identifier-syntax">kinds_required</span><span class="plain-syntax">, </span><span class="identifier-syntax">tc_problem_kit</span><span class="plain-syntax"> *</span><span class="identifier-syntax">tck</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">LOGIF</span><span class="plain-syntax">(</span><span class="identifier-syntax">MATCHING</span><span class="plain-syntax">, </span><span class="string-syntax">"Typecheck %u '==' %u\n"</span><span class="plain-syntax">, </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1]);</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">K_understanding</span><span class="plain-syntax">) && (</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">K_understanding</span><span class="plain-syntax">)) &&</span>
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<span class="plain-syntax"> (</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">K_text</span><span class="plain-syntax">))) {</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">LOGIF</span><span class="plain-syntax">(</span><span class="identifier-syntax">MATCHING</span><span class="plain-syntax">, </span><span class="string-syntax">"No!\n"</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">StandardProblems::tcp_problem</span><span class="plain-syntax">(</span><span class="identifier-syntax">_p_</span><span class="plain-syntax">(</span><span class="identifier-syntax">PM_TextIsNotTopic</span><span class="plain-syntax">), </span><span class="identifier-syntax">tck</span><span class="plain-syntax">,</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"though they look the same, because both are written in double "</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"quotes, text values can't in fact be used as topics, so it's "</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"impossible to store this piece of text in that location."</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">NEVER_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> }</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">PluginCalls::typecheck_equality</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1]))</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">ALWAYS_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">Kinds::Behaviour::is_object</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0])) &&</span>
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<span class="plain-syntax"> (</span><span class="identifier-syntax">Properties::can_name_coincide_with_kind</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1])))</span>
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<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="8-terr.html#SP2_1" class="named-paragraph-link"><span class="named-paragraph">Apply rule for "is" applied to an object and a value</span><span class="named-paragraph-number">2.1</span></a></span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">else</span><span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">K_understanding</span><span class="plain-syntax">) && (</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">K_understanding</span><span class="plain-syntax">)) &&</span>
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<span class="plain-syntax"> (</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">K_snippet</span><span class="plain-syntax">)))</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">ALWAYS_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">else</span><span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">K_understanding</span><span class="plain-syntax">) && (</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">K_understanding</span><span class="plain-syntax">)) &&</span>
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<span class="plain-syntax"> (</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">K_snippet</span><span class="plain-syntax">)))</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">ALWAYS_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">else</span><span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">K_text</span><span class="plain-syntax">)) &&</span>
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<span class="plain-syntax"> (</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">K_response</span><span class="plain-syntax">)))</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">ALWAYS_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">else</span>
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<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="8-terr.html#SP2_2" class="named-paragraph-link"><span class="named-paragraph">Allow comparison only where left domain and right domain are not disjoint</span><span class="named-paragraph-number">2.2</span></a></span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">ALWAYS_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax">}</span>
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</pre>
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<p class="commentary firstcommentary"><a id="SP2_1" class="paragraph-anchor"></a><b>§2.1. </b>This case is only separated in order to provide a better problem message
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for a fairly common mistake:
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</p>
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<p class="commentary"><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Apply rule for "is" applied to an object and a value</span><span class="named-paragraph-number">2.1</span></span><span class="comment-syntax"> =</span>
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</p>
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<pre class="displayed-code all-displayed-code code-font">
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<span class="plain-syntax"> </span><span class="identifier-syntax">property</span><span class="plain-syntax"> *</span><span class="identifier-syntax">prn</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Properties::property_with_same_name_as</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1]);</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">prn</span><span class="plain-syntax"> == </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">tck</span><span class="plain-syntax">-></span><span class="identifier-syntax">log_to_I6_text</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">LOG</span><span class="plain-syntax">(</span><span class="string-syntax">"Comparison of object with %u value\n"</span><span class="plain-syntax">, </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1]);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">Problems::quote_kind</span><span class="plain-syntax">(4, </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1]);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">StandardProblems::tcp_problem</span><span class="plain-syntax">(</span><span class="identifier-syntax">_p_</span><span class="plain-syntax">(</span><span class="identifier-syntax">PM_NonPropertyCompared</span><span class="plain-syntax">), </span><span class="identifier-syntax">tck</span><span class="plain-syntax">,</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"taken literally that says that an object is the same as a "</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"value. Maybe you intended to say that the object "</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"has a property - but right now %4 is not yet a property; if you "</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"want to use it as one, you'll need to say so. (You can turn a "</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"kind of value - say, 'colour' - into a property by writing - "</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"say - 'A thing has a colour.')"</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">NEVER_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> }</span>
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</pre>
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<ul class="endnotetexts"><li>This code is used in <a href="8-terr.html#SP2">§2</a>.</li></ul>
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<p class="commentary firstcommentary"><a id="SP2_2" class="paragraph-anchor"></a><b>§2.2. </b>With comparisons there is no restriction on the two kinds except that they
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must match each other; \({\it is}(t, s)\) is allowed if \(K(t)\subseteq K(s)\) or
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vice versa. So rules and rulebooks are comparable, for instance, but numbers
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and scenes are not.
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</p>
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<p class="commentary"><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Allow comparison only where left domain and right domain are not disjoint</span><span class="named-paragraph-number">2.2</span></span><span class="comment-syntax"> =</span>
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</p>
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<pre class="displayed-code all-displayed-code code-font">
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="8-terr.html#SP3" class="function-link"><span class="function-syntax">EqualityDetails::both_terms_of_same_construction</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">CON_rule</span><span class="plain-syntax">))</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">ALWAYS_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="8-terr.html#SP3" class="function-link"><span class="function-syntax">EqualityDetails::both_terms_of_same_construction</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">CON_rulebook</span><span class="plain-syntax">))</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">ALWAYS_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="8-terr.html#SP3" class="function-link"><span class="function-syntax">EqualityDetails::both_terms_of_same_construction</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">CON_activity</span><span class="plain-syntax">))</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">ALWAYS_MATCH</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">Kinds::compatible</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1]) == </span><span class="identifier-syntax">NEVER_MATCH</span><span class="plain-syntax">) &&</span>
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<span class="plain-syntax"> (</span><span class="identifier-syntax">Kinds::compatible</span><span class="plain-syntax">(</span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0]) == </span><span class="identifier-syntax">NEVER_MATCH</span><span class="plain-syntax">)) {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">tck</span><span class="plain-syntax">-></span><span class="identifier-syntax">log_to_I6_text</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">"Unable to compare %u with %u\n"</span><span class="plain-syntax">, </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">kinds_of_terms</span><span class="plain-syntax">[1]);</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">NEVER_MATCH_SAYING_WHY_NOT</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> }</span>
|
|
</pre>
|
|
<ul class="endnotetexts"><li>This code is used in <a href="8-terr.html#SP2">§2</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP3" class="paragraph-anchor"></a><b>§3. </b></p>
|
|
|
|
<pre class="displayed-code all-displayed-code code-font">
|
|
<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">EqualityDetails::both_terms_of_same_construction</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">EqualityDetails::both_terms_of_same_construction</span></span>:<br/><a href="8-terr.html#SP2_2">§2.2</a></span></button><span class="plain-syntax">(</span><span class="identifier-syntax">kind</span><span class="plain-syntax"> *</span><span class="identifier-syntax">k0</span><span class="plain-syntax">, </span><span class="identifier-syntax">kind</span><span class="plain-syntax"> *</span><span class="identifier-syntax">k1</span><span class="plain-syntax">, </span><span class="identifier-syntax">kind_constructor</span><span class="plain-syntax"> *</span><span class="identifier-syntax">cons</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::get_construct</span><span class="plain-syntax">(</span><span class="identifier-syntax">k0</span><span class="plain-syntax">) == </span><span class="identifier-syntax">cons</span><span class="plain-syntax">) && (</span><span class="identifier-syntax">Kinds::get_construct</span><span class="plain-syntax">(</span><span class="identifier-syntax">k1</span><span class="plain-syntax">) == </span><span class="identifier-syntax">cons</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><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>
|
|
<p class="commentary firstcommentary"><a id="SP4" class="paragraph-anchor"></a><b>§4. Assertion. </b>In general values differ, and cannot be equated by fiat. But an exception is
|
|
setting a global variable.
|
|
</p>
|
|
|
|
<pre class="displayed-code all-displayed-code code-font">
|
|
<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">EqualityDetails::assert</span><button class="popup" onclick="togglePopup('usagePopup4')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup4">Usage of <span class="code-font"><span class="function-syntax">EqualityDetails::assert</span></span>:<br/><a href="8-terr.html#SP1">§1</a></span></button><span class="plain-syntax">(</span><span class="identifier-syntax">bp_family</span><span class="plain-syntax"> *</span><span class="identifier-syntax">self</span><span class="plain-syntax">, </span><span class="identifier-syntax">binary_predicate</span><span class="plain-syntax"> *</span><span class="identifier-syntax">bp</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">inference_subject</span><span class="plain-syntax"> *</span><span class="identifier-syntax">infs0</span><span class="plain-syntax">, </span><span class="identifier-syntax">parse_node</span><span class="plain-syntax"> *</span><span class="identifier-syntax">spec0</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">inference_subject</span><span class="plain-syntax"> *</span><span class="identifier-syntax">infs1</span><span class="plain-syntax">, </span><span class="identifier-syntax">parse_node</span><span class="plain-syntax"> *</span><span class="identifier-syntax">spec1</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">Lvalues::is_actual_NONLOCAL_VARIABLE</span><span class="plain-syntax">(</span><span class="identifier-syntax">spec0</span><span class="plain-syntax">)) {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">nonlocal_variable</span><span class="plain-syntax"> *</span><span class="identifier-syntax">q</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Node::get_constant_nonlocal_variable</span><span class="plain-syntax">(</span><span class="identifier-syntax">spec0</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">allowed</span><span class="plain-syntax"> = </span><span class="identifier-syntax">TRUE</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">prevailing_mood</span><span class="plain-syntax"> != </span><span class="identifier-syntax">UNKNOWN_CE</span><span class="plain-syntax">) && (</span><span class="identifier-syntax">prevailing_mood</span><span class="plain-syntax"> != </span><span class="identifier-syntax">LIKELY_CE</span><span class="plain-syntax">))</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">allowed</span><span class="plain-syntax"> = </span><span class="identifier-syntax">FALSE</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">NonlocalVariables::is_constant</span><span class="plain-syntax">(</span><span class="identifier-syntax">q</span><span class="plain-syntax">)) && (</span><span class="identifier-syntax">prevailing_mood</span><span class="plain-syntax"> == </span><span class="identifier-syntax">CERTAIN_CE</span><span class="plain-syntax">))</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">allowed</span><span class="plain-syntax"> = </span><span class="identifier-syntax">TRUE</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">allowed</span><span class="plain-syntax"> == </span><span class="identifier-syntax">FALSE</span><span class="plain-syntax">)</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">StandardProblems::sentence_problem</span><span class="plain-syntax">(</span><span class="identifier-syntax">Task::syntax_tree</span><span class="plain-syntax">(), </span><span class="identifier-syntax">_p_</span><span class="plain-syntax">(</span><span class="identifier-syntax">PM_CantQualifyVariableValues</span><span class="plain-syntax">),</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"a variable can only be given its value straightforwardly or "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"qualified by 'usually'"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"not with 'always', 'seldom' or 'never'."</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">else</span><span class="plain-syntax"> </span><span class="identifier-syntax">PropertyInferences::draw</span><span class="plain-syntax">(</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">NonlocalVariables::to_subject</span><span class="plain-syntax">(</span><span class="identifier-syntax">q</span><span class="plain-syntax">), </span><span class="identifier-syntax">P_variable_initial_value</span><span class="plain-syntax">, </span><span class="identifier-syntax">spec1</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>
|
|
<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>
|
|
<p class="commentary firstcommentary"><a id="SP5" class="paragraph-anchor"></a><b>§5. Compilation. </b>Since we are compiling to I6, which is itself a C-level programming
|
|
language, it looks at first as if we can compile is into <span class="extract"><span class="extract-syntax">==</span></span> when
|
|
testing equality and <span class="extract"><span class="extract-syntax">=</span></span> when asserting it: thus
|
|
</p>
|
|
|
|
<blockquote>
|
|
<p>now the score is 10;</p>
|
|
</blockquote>
|
|
|
|
<blockquote>
|
|
<p>if the score is 10, ...</p>
|
|
</blockquote>
|
|
|
|
<p class="commentary">would compile to <span class="extract"><span class="extract-syntax">score = 10;</span></span> and <span class="extract"><span class="extract-syntax">if (score == 10) ...</span></span> respectively.
|
|
</p>
|
|
|
|
<p class="commentary">But there are three problems with this simplistic approach to "A is B".
|
|
</p>
|
|
|
|
<ul class="items"><li>(a) Sometimes "now A is B" must set a property of A, which does not
|
|
change, rather than making A equal to B; and similarly for testing.
|
|
</li><li>(b) Sometimes A is reference to a value stored in some data structure
|
|
other than a local or global variable: for example, in "now entry 3 of
|
|
the passenger list is 208", where A is "entry 3 of the passenger list".
|
|
Access to this value is via I6 routines in the template, and the form of
|
|
what we compile has to be different depending on whether we are reading
|
|
or writing.
|
|
</li><li>(c) Sometimes the values in question are block values, that is, they are
|
|
stored as pointers to blocks of data on the heap at run-time. If we compile
|
|
"now T is X", where T is a text variable and X is some piece of text, we
|
|
cannot simply copy the pointers: T needs to hold a fresh, independent copy of
|
|
the text referred to by X.
|
|
</li></ul>
|
|
<p class="commentary">Problem (a) is easily detected by looking at the kinds of value of A and B.
|
|
To handle problems (b) and (c), we use a general framework in which the
|
|
schema is a function of both the storage class of A and the kinds of value
|
|
of both A and B.
|
|
</p>
|
|
|
|
<pre class="displayed-code all-displayed-code code-font">
|
|
<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">EqualityDetails::schema</span><button class="popup" onclick="togglePopup('usagePopup5')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup5">Usage of <span class="code-font"><span class="function-syntax">EqualityDetails::schema</span></span>:<br/><a href="8-terr.html#SP1">§1</a></span></button><span class="plain-syntax">(</span><span class="identifier-syntax">bp_family</span><span class="plain-syntax"> *</span><span class="identifier-syntax">self</span><span class="plain-syntax">, </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">task</span><span class="plain-syntax">, </span><span class="identifier-syntax">binary_predicate</span><span class="plain-syntax"> *</span><span class="identifier-syntax">bp</span><span class="plain-syntax">, </span><span class="identifier-syntax">annotated_i6_schema</span><span class="plain-syntax"> *</span><span class="identifier-syntax">asch</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">st</span><span class="plain-syntax">[2];</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">st</span><span class="plain-syntax">[0] = </span><span class="identifier-syntax">Cinders::kind_of_term</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">pt0</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">st</span><span class="plain-syntax">[1] = </span><span class="identifier-syntax">Cinders::kind_of_term</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">pt1</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::is_object</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[0])) &&</span>
|
|
<span class="plain-syntax"> (</span><span class="identifier-syntax">Properties::can_name_coincide_with_kind</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[1])) && (</span><span class="identifier-syntax">Properties::property_with_same_name_as</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[1])))</span>
|
|
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="8-terr.html#SP5_1" class="named-paragraph-link"><span class="named-paragraph">Handle the case of setting a property of A separately</span><span class="named-paragraph-number">5.1</span></a></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::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">K_response</span><span class="plain-syntax">)) && (</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">K_text</span><span class="plain-syntax">)))</span>
|
|
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="8-terr.html#SP5_2" class="named-paragraph-link"><span class="named-paragraph">Handle the case of setting a response separately</span><span class="named-paragraph-number">5.2</span></a></span><span class="plain-syntax">;</span>
|
|
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">switch</span><span class="plain-syntax"> (</span><span class="identifier-syntax">task</span><span class="plain-syntax">) {</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">case</span><span class="plain-syntax"> </span><span class="identifier-syntax">TEST_ATOM_TASK:</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">st</span><span class="plain-syntax">[0]) && (</span><span class="identifier-syntax">st</span><span class="plain-syntax">[1]))</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Calculus::Schemas::modify</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"%S"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">EqualitySchemas::interpret_equality</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">st</span><span class="plain-syntax">[1]));</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">else</span><span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">problem_count</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">LOG</span><span class="plain-syntax">(</span><span class="string-syntax">"$0 and $0; %u and %u\n"</span><span class="plain-syntax">, &(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">pt0</span><span class="plain-syntax">), &(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">pt1</span><span class="plain-syntax">), </span><span class="identifier-syntax">st</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">st</span><span class="plain-syntax">[1]);</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">StandardProblems::sentence_problem</span><span class="plain-syntax">(</span><span class="identifier-syntax">Task::syntax_tree</span><span class="plain-syntax">(), </span><span class="identifier-syntax">_p_</span><span class="plain-syntax">(</span><span class="identifier-syntax">BelievedImpossible</span><span class="plain-syntax">),</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"that would involve comparing things which don't mean "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"anything to me"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"so I'm lost."</span><span class="plain-syntax">);</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><span class="reserved-syntax">case</span><span class="plain-syntax"> </span><span class="identifier-syntax">NOW_ATOM_FALSE_TASK:</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">break</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">case</span><span class="plain-syntax"> </span><span class="identifier-syntax">NOW_ATOM_TRUE_TASK:</span><span class="plain-syntax"> {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">node_type_t</span><span class="plain-syntax"> </span><span class="identifier-syntax">storage_class</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Lvalues::get_storage_form</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">pt0</span><span class="plain-syntax">.</span><span class="identifier-syntax">constant</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">storage_class</span><span class="plain-syntax"> == </span><span class="identifier-syntax">UNKNOWN_NT</span><span class="plain-syntax">) &&</span>
|
|
<span class="plain-syntax"> (</span><span class="identifier-syntax">Kinds::get_construct</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[0]) == </span><span class="identifier-syntax">CON_property</span><span class="plain-syntax">))</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">storage_class</span><span class="plain-syntax"> = </span><span class="identifier-syntax">PROPERTY_VALUE_NT</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="8-terr.html#SP5_4" class="named-paragraph-link"><span class="named-paragraph">Make a further check that kinds permit this assignment</span><span class="named-paragraph-number">5.4</span></a></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">storage_class</span><span class="plain-syntax"> == </span><span class="identifier-syntax">UNKNOWN_NT</span><span class="plain-syntax">) {</span>
|
|
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="8-terr.html#SP5_5" class="named-paragraph-link"><span class="named-paragraph">Issue problem message for being unable to set equal</span><span class="named-paragraph-number">5.5</span></a></span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> } </span><span class="reserved-syntax">else</span><span class="plain-syntax"> {</span>
|
|
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="8-terr.html#SP5_3" class="named-paragraph-link"><span class="named-paragraph">Exceptional case of setting the "player" global variable</span><span class="named-paragraph-number">5.3</span></a></span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Calculus::Schemas::modify</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"%s"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">CompileLvalues::interpret_store</span><span class="plain-syntax">(</span><span class="identifier-syntax">storage_class</span><span class="plain-syntax">, </span><span class="identifier-syntax">st</span><span class="plain-syntax">[0], </span><span class="identifier-syntax">st</span><span class="plain-syntax">[1], </span><span class="constant-syntax">0</span><span class="plain-syntax">));</span>
|
|
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="8-terr.html#SP5_6" class="named-paragraph-link"><span class="named-paragraph">Add kind-checking code for run-time checking</span><span class="named-paragraph-number">5.6</span></a></span><span class="plain-syntax">;</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>
|
|
<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>
|
|
<p class="commentary firstcommentary"><a id="SP5_1" class="paragraph-anchor"></a><b>§5.1. </b>So here is the exceptional case (a) mentioned above. Suppose we have:
|
|
</p>
|
|
|
|
<blockquote>
|
|
<p>if the lantern is bright, ...</p>
|
|
</blockquote>
|
|
|
|
<p class="commentary">where "bright" is one value of "luminance", which is both a kind of value
|
|
and also a property. We then want to test if the luminance property of the
|
|
lantern equals the constant value "bright"; and similarly for "now the
|
|
lantern is bright".
|
|
</p>
|
|
|
|
<p class="commentary"><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Handle the case of setting a property of A separately</span><span class="named-paragraph-number">5.1</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">property</span><span class="plain-syntax"> *</span><span class="identifier-syntax">prn</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Properties::property_with_same_name_as</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[1]);</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">switch</span><span class="plain-syntax"> (</span><span class="identifier-syntax">task</span><span class="plain-syntax">) {</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">case</span><span class="plain-syntax"> </span><span class="identifier-syntax">TEST_ATOM_TASK:</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Calculus::Schemas::modify</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"*1.%n == *2"</span><span class="plain-syntax">, </span><span class="identifier-syntax">RTProperties::iname</span><span class="plain-syntax">(</span><span class="identifier-syntax">prn</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><span class="reserved-syntax">case</span><span class="plain-syntax"> </span><span class="identifier-syntax">NOW_ATOM_FALSE_TASK:</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">break</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">case</span><span class="plain-syntax"> </span><span class="identifier-syntax">NOW_ATOM_TRUE_TASK:</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Calculus::Schemas::modify</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"*1.%n = *2"</span><span class="plain-syntax">, </span><span class="identifier-syntax">RTProperties::iname</span><span class="plain-syntax">(</span><span class="identifier-syntax">prn</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>
|
|
<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>
|
|
</pre>
|
|
<ul class="endnotetexts"><li>This code is used in <a href="8-terr.html#SP5">§5</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP5_2" class="paragraph-anchor"></a><b>§5.2. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Handle the case of setting a response separately</span><span class="named-paragraph-number">5.2</span></span><span class="comment-syntax"> =</span>
|
|
</p>
|
|
|
|
<pre class="displayed-code all-displayed-code code-font">
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">switch</span><span class="plain-syntax"> (</span><span class="identifier-syntax">task</span><span class="plain-syntax">) {</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">case</span><span class="plain-syntax"> </span><span class="identifier-syntax">TEST_ATOM_TASK:</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">StandardProblems::sentence_problem</span><span class="plain-syntax">(</span><span class="identifier-syntax">Task::syntax_tree</span><span class="plain-syntax">(), </span><span class="identifier-syntax">_p_</span><span class="plain-syntax">(</span><span class="identifier-syntax">PM_ResponseComparisonUnsafe</span><span class="plain-syntax">),</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"for complicated internal reasons this comparison isn't safe to perform"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"and might give you a falsely negative result. To avoid what might "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"be misleading, you aren't allowed to compare a response to text."</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">break</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">case</span><span class="plain-syntax"> </span><span class="identifier-syntax">NOW_ATOM_FALSE_TASK:</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">break</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">case</span><span class="plain-syntax"> </span><span class="identifier-syntax">NOW_ATOM_TRUE_TASK:</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Calculus::Schemas::modify</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"BlkValueCopy(ResponseTexts-->((*1)-1), *^2)"</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>
|
|
<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>
|
|
</pre>
|
|
<ul class="endnotetexts"><li>This code is used in <a href="8-terr.html#SP5">§5</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP5_3" class="paragraph-anchor"></a><b>§5.3. </b>A little bit of support within Inform to help the template layer.
|
|
</p>
|
|
|
|
<p class="commentary"><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Exceptional case of setting the "player" global variable</span><span class="named-paragraph-number">5.3</span></span><span class="comment-syntax"> =</span>
|
|
</p>
|
|
|
|
<pre class="displayed-code all-displayed-code code-font">
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">nonlocal_variable</span><span class="plain-syntax"> *</span><span class="identifier-syntax">nlv</span><span class="plain-syntax"> =</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Lvalues::get_nonlocal_variable_if_any</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">pt0</span><span class="plain-syntax">.</span><span class="identifier-syntax">constant</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">nlv</span><span class="plain-syntax">) && (</span><span class="identifier-syntax">NonlocalVariables::must_be_constant</span><span class="plain-syntax">(</span><span class="identifier-syntax">nlv</span><span class="plain-syntax">))) {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</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>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">NonlocalVariables::warn_about_change</span><span class="plain-syntax">(</span><span class="identifier-syntax">nlv</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">exotica</span><span class="plain-syntax"> = </span><span class="identifier-syntax">RTVariables::get_write_schema</span><span class="plain-syntax">(</span><span class="identifier-syntax">nlv</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">exotica</span><span class="plain-syntax">) {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Calculus::Schemas::modify</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"%S"</span><span class="plain-syntax">, </span><span class="identifier-syntax">exotica</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>This code is used in <a href="8-terr.html#SP5">§5</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP5_4" class="paragraph-anchor"></a><b>§5.4. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Make a further check that kinds permit this assignment</span><span class="named-paragraph-number">5.4</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">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">Kinds::compatible</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">st</span><span class="plain-syntax">[0]) == </span><span class="identifier-syntax">NEVER_MATCH</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">dst</span><span class="plain-syntax">[2];</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">dst</span><span class="plain-syntax">[0] = </span><span class="identifier-syntax">Kinds::dereference_properties</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[0]);</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">dst</span><span class="plain-syntax">[1] = </span><span class="identifier-syntax">Kinds::dereference_properties</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[1]);</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">Kinds::compatible</span><span class="plain-syntax">(</span><span class="identifier-syntax">dst</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">dst</span><span class="plain-syntax">[0]) == </span><span class="identifier-syntax">NEVER_MATCH</span><span class="plain-syntax">) {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Problems::quote_source</span><span class="plain-syntax">(1, </span><span class="identifier-syntax">current_sentence</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Problems::quote_kind</span><span class="plain-syntax">(2, </span><span class="identifier-syntax">st</span><span class="plain-syntax">[1]);</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Problems::quote_kind</span><span class="plain-syntax">(3, </span><span class="identifier-syntax">st</span><span class="plain-syntax">[0]);</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">StandardProblems::handmade_problem</span><span class="plain-syntax">(</span><span class="identifier-syntax">Task::syntax_tree</span><span class="plain-syntax">(), </span><span class="identifier-syntax">_p_</span><span class="plain-syntax">(</span><span class="identifier-syntax">BelievedImpossible</span><span class="plain-syntax">));</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Problems::issue_problem_segment</span><span class="plain-syntax">(</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"In the line %1, you seem to be asking me to put %2 into %3, "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"which can't safely be done."</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Problems::issue_problem_end</span><span class="plain-syntax">();</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</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>
|
|
<span class="plain-syntax"> }</span>
|
|
</pre>
|
|
<ul class="endnotetexts"><li>This code is used in <a href="8-terr.html#SP5">§5</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP5_5" class="paragraph-anchor"></a><b>§5.5. </b>Rather than just returning <span class="extract"><span class="extract-syntax">FALSE</span></span> for a generic problem message, we issue
|
|
one that's more helpfully specific and return <span class="extract"><span class="extract-syntax">TRUE</span></span>.
|
|
</p>
|
|
|
|
<p class="commentary"><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Issue problem message for being unable to set equal</span><span class="named-paragraph-number">5.5</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">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">Rvalues::to_instance</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">pt0</span><span class="plain-syntax">.</span><span class="identifier-syntax">constant</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::is_object</span><span class="plain-syntax">(</span><span class="identifier-syntax">Specifications::to_kind</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">pt0</span><span class="plain-syntax">.</span><span class="identifier-syntax">constant</span><span class="plain-syntax">)))</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">StandardProblems::sentence_problem</span><span class="plain-syntax">(</span><span class="identifier-syntax">Task::syntax_tree</span><span class="plain-syntax">(), </span><span class="identifier-syntax">_p_</span><span class="plain-syntax">(</span><span class="identifier-syntax">PM_CantEquateValues</span><span class="plain-syntax">),</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"equality is not something I can change"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"so either those are already the same or are different, and I "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"can't alter matters."</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">else</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">StandardProblems::sentence_problem</span><span class="plain-syntax">(</span><span class="identifier-syntax">Task::syntax_tree</span><span class="plain-syntax">(), </span><span class="identifier-syntax">_p_</span><span class="plain-syntax">(</span><span class="identifier-syntax">PM_CantChangeNamedConstant</span><span class="plain-syntax">),</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"I can't change that"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"because it is a name for a constant value. Some named values, "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"like 'the score', can be changed, because they were defined "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"as values that vary. But others are fixed. If we write 'The "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"oak tree can be sturdy, lightning-struck or leaning.', for "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"instance, then 'sturdy' is a name for a value which is fixed, "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"just as the number '7' is fixed."</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> }</span>
|
|
</pre>
|
|
<ul class="endnotetexts"><li>This code is used in <a href="8-terr.html#SP5">§5</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP5_6" class="paragraph-anchor"></a><b>§5.6. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Add kind-checking code for run-time checking</span><span class="named-paragraph-number">5.6</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">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">Kinds::compatible</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[1], </span><span class="identifier-syntax">st</span><span class="plain-syntax">[0]) == </span><span class="identifier-syntax">SOMETIMES_MATCH</span><span class="plain-syntax">) &&</span>
|
|
<span class="plain-syntax"> (</span><span class="identifier-syntax">Kinds::Behaviour::is_subkind_of_object</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[0]))) {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">TEMPORARY_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">TEMP</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">TEMP</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"; if (~~(*1 ofclass %n)) RunTimeProblem(RTP_WRONGASSIGNEDKIND, *1, \"*?\", \""</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">RTKindDeclarations::iname</span><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[0]));</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Kinds::Textual::write</span><span class="plain-syntax">(</span><span class="identifier-syntax">TEMP</span><span class="plain-syntax">, </span><span class="identifier-syntax">st</span><span class="plain-syntax">[0]);</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">WRITE_TO</span><span class="plain-syntax">(</span><span class="identifier-syntax">TEMP</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">Calculus::Schemas::append</span><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="identifier-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"%S"</span><span class="plain-syntax">, </span><span class="identifier-syntax">TEMP</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">TEMP</span><span class="plain-syntax">)</span>
|
|
<span class="plain-syntax"> }</span>
|
|
</pre>
|
|
<ul class="endnotetexts"><li>This code is used in <a href="8-terr.html#SP5">§5</a>.</li></ul>
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