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<!--Weave of 'The Equality Relation' generated by Inweb-->
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<div class="breadcrumbs">
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<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="../compiler.html">Inform7 Modules</a></li><li><a href="index.html">core</a></li><li><a href="index.html#12">Chapter 12: Use of Propositions</a></li><li><b>The Equality Relation</b></li></ul></div>
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<p class="purpose">To define that prince among predicates, the equality relation.</p>
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<ul class="toc"><li><a href="12-ter.html#SP2">§2. Initial stock</a></li><li><a href="12-ter.html#SP3">§3. Second stock</a></li><li><a href="12-ter.html#SP4">§4. Typechecking</a></li><li><a href="12-ter.html#SP6">§6. Assertion</a></li><li><a href="12-ter.html#SP7">§7. Compilation</a></li><li><a href="12-ter.html#SP8">§8. Problem message text</a></li></ul><hr class="tocbar">
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<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>§1. </b>This predicate expresses the meaning of \(a=b\), and plays a very special role
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in our calculus.
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</p>
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<pre class="displayed-code all-displayed-code code-font">
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<span class="identifier-syntax">binary_predicate</span><span class="plain-syntax"> *</span><span class="identifier-syntax">R_equality</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
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<span class="identifier-syntax">binary_predicate</span><span class="plain-syntax"> *</span><span class="identifier-syntax">a_has_b_predicate</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><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. Initial stock. </b>This relation is hard-wired in, and it is made in a slightly special way
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since (alone among binary predicates) it has no distinct reversal.
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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">void</span><span class="plain-syntax"> </span><span class="function-syntax">Calculus::Equality::REL_create_initial_stock</span><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">R_equality</span><span class="plain-syntax"> = </span><span class="identifier-syntax">BinaryPredicates::make_equality</span><span class="plain-syntax">();</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">BinaryPredicates::set_index_details</span><span class="plain-syntax">(</span><span class="identifier-syntax">R_equality</span><span class="plain-syntax">, </span><span class="string-syntax">"value"</span><span class="plain-syntax">, </span><span class="string-syntax">"value"</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">word_assemblage</span><span class="plain-syntax"> </span><span class="identifier-syntax">wa</span><span class="plain-syntax"> = </span><span class="identifier-syntax">PreformUtilities::merge</span><span class="plain-syntax">(</span><span class="function-syntax"><relation-name-formal></span><span class="plain-syntax">, </span><span class="constant-syntax">0</span><span class="plain-syntax">,</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">PreformUtilities::wording</span><span class="plain-syntax">(</span><span class="function-syntax"><relation-names></span><span class="plain-syntax">, </span><span class="constant-syntax">EQUALITY_RELATION_NAME</span><span class="plain-syntax">));</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">wording</span><span class="plain-syntax"> </span><span class="identifier-syntax">AW</span><span class="plain-syntax"> = </span><span class="identifier-syntax">WordAssemblages::to_wording</span><span class="plain-syntax">(&</span><span class="identifier-syntax">wa</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">Nouns::new_proper_noun</span><span class="plain-syntax">(</span><span class="identifier-syntax">AW</span><span class="plain-syntax">, </span><span class="identifier-syntax">NEUTER_GENDER</span><span class="plain-syntax">, </span><span class="identifier-syntax">ADD_TO_LEXICON_NTOPT</span><span class="plain-syntax">,</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">MISCELLANEOUS_MC</span><span class="plain-syntax">, </span><a href="14-rv.html#SP1" class="function-link"><span class="function-syntax">Rvalues::from_binary_predicate</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">R_equality</span><span class="plain-syntax">),</span>
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<span class="plain-syntax"> </span><a href="1-wtc.html#SP6" class="function-link"><span class="function-syntax">Task::language_of_syntax</span></a><span class="plain-syntax">());</span>
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<span class="plain-syntax"> #</span><span class="identifier-syntax">ifndef</span><span class="plain-syntax"> </span><span class="identifier-syntax">IF_MODULE</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">a_has_b_predicate</span><span class="plain-syntax"> =</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">BinaryPredicates::make_pair</span><span class="plain-syntax">(</span><span class="identifier-syntax">SPATIAL_KBP</span><span class="plain-syntax">,</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">BinaryPredicates::full_new_term</span><span class="plain-syntax">(</span><span class="identifier-syntax">NULL</span><span class="plain-syntax">, </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">, </span><span class="identifier-syntax">EMPTY_WORDING</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="identifier-syntax">BinaryPredicates::new_term</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="identifier-syntax">I</span><span class="string-syntax">"has"</span><span class="plain-syntax">, </span><span class="identifier-syntax">I</span><span class="string-syntax">"is-had-by"</span><span class="plain-syntax">,</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">, </span><span class="identifier-syntax">NULL</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="identifier-syntax">PreformUtilities::wording</span><span class="plain-syntax">(</span><span class="function-syntax"><relation-names></span><span class="plain-syntax">, </span><span class="constant-syntax">POSSESSION_RELATION_NAME</span><span class="plain-syntax">));</span>
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<span class="plain-syntax"> #</span><span class="identifier-syntax">endif</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="SP3" class="paragraph-anchor"></a><b>§3. Second stock. </b>There is none, of course.
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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">void</span><span class="plain-syntax"> </span><span class="function-syntax">Calculus::Equality::REL_create_second_stock</span><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>
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</pre>
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<p class="commentary firstcommentary"><a id="SP4" class="paragraph-anchor"></a><b>§4. 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">Calculus::Equality::REL_typecheck</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="reserved-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><a href="2-si.html#SP6" class="function-link"><span class="function-syntax">StandardProblems::tcp_problem</span></a><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><a href="26-pc.html#SP7" class="function-link"><span class="function-syntax">Plugins::Call::typecheck_equality</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>
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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><a href="15-cp.html#SP5" class="function-link"><span class="function-syntax">Properties::Conditions::name_can_coincide_with_property</span></a><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="12-ter.html#SP4_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">4.1</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="12-ter.html#SP4_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">4.2</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="SP4_1" class="paragraph-anchor"></a><b>§4.1. </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">4.1</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="reserved-syntax">property</span><span class="plain-syntax"> *</span><span class="identifier-syntax">prn</span><span class="plain-syntax"> = </span><a href="15-cp.html#SP5" class="function-link"><span class="function-syntax">Properties::Conditions::get_coinciding_property</span></a><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="element-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><a href="2-sq.html#SP3" class="function-link"><span class="function-syntax">Problems::quote_kind</span></a><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><a href="2-si.html#SP6" class="function-link"><span class="function-syntax">StandardProblems::tcp_problem</span></a><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>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"taken literally that says that an object is the same as a "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"value. Maybe you intended to say that the object "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"has a property - but right now %4 is not yet a property; if you "</span>
|
|
<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>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"kind of value - say, 'colour' - into a property by writing - "</span>
|
|
<span class="plain-syntax"> </span><span class="string-syntax">"say - 'A thing has a colour.')"</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">NEVER_MATCH</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> }</span>
|
|
</pre>
|
|
<ul class="endnotetexts"><li>This code is used in <a href="12-ter.html#SP4">§4</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP4_2" class="paragraph-anchor"></a><b>§4.2. </b>With comparisons there is no restriction on the two kinds except that they
|
|
must match each other; \({\it is}(t, s)\) is allowed if \(K(t)\subseteq K(s)\) or
|
|
vice versa. So rules and rulebooks are comparable, for instance, but numbers
|
|
and scenes are not.
|
|
</p>
|
|
|
|
<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">4.2</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">if</span><span class="plain-syntax"> (</span><a href="12-ter.html#SP5" class="function-link"><span class="function-syntax">Calculus::Equality::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>
|
|
<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>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="12-ter.html#SP5" class="function-link"><span class="function-syntax">Calculus::Equality::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>
|
|
<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>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="12-ter.html#SP5" class="function-link"><span class="function-syntax">Calculus::Equality::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>
|
|
<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>
|
|
<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>
|
|
<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>
|
|
<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="element-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="12-ter.html#SP4">§4</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP5" class="paragraph-anchor"></a><b>§5. </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">Calculus::Equality::both_terms_of_same_construction</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">Calculus::Equality::both_terms_of_same_construction</span></span>:<br/><a href="12-ter.html#SP4_2">§4.2</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="SP6" class="paragraph-anchor"></a><b>§6. 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">Calculus::Equality::REL_assert</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="reserved-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="reserved-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><a href="14-lv.html#SP8" class="function-link"><span class="function-syntax">Lvalues::is_actual_NONLOCAL_VARIABLE</span></a><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">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><a href="6-nv.html#SP21" class="function-link"><span class="function-syntax">NonlocalVariables::is_constant</span></a><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><a href="1-wtc.html#SP6" class="function-link"><span class="function-syntax">Task::syntax_tree</span></a><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><a href="16-in.html#SP8" class="function-link"><span class="function-syntax">World::Inferences::draw_property</span></a><span class="plain-syntax">(</span>
|
|
<span class="plain-syntax"> </span><a href="6-nv.html#SP14" class="function-link"><span class="function-syntax">NonlocalVariables::get_knowledge</span></a><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="SP7" class="paragraph-anchor"></a><b>§7. 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">Calculus::Equality::REL_compile</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="reserved-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><a href="12-cad.html#SP6" class="function-link"><span class="function-syntax">Calculus::Deferrals::Cinders::kind_of_value_of_term</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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><a href="12-cad.html#SP6" class="function-link"><span class="function-syntax">Calculus::Deferrals::Cinders::kind_of_value_of_term</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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><a href="15-cp.html#SP5" class="function-link"><span class="function-syntax">Properties::Conditions::name_can_coincide_with_property</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">st</span><span class="plain-syntax">[1])) && (</span><a href="15-cp.html#SP5" class="function-link"><span class="function-syntax">Properties::Conditions::get_coinciding_property</span></a><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="12-ter.html#SP7_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">7.1</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="12-ter.html#SP7_2" class="named-paragraph-link"><span class="named-paragraph">Handle the case of setting a response separately</span><span class="named-paragraph-number">7.2</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><a href="12-is.html#SP3_1" class="function-link"><span class="function-syntax">Calculus::Schemas::modify</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"%S"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><a href="13-rsfk.html#SP7" class="function-link"><span class="function-syntax">Kinds::RunTime::interpret_test_equality</span></a><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="element-syntax">pt0</span><span class="plain-syntax">), &(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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><a href="1-wtc.html#SP6" class="function-link"><span class="function-syntax">Task::syntax_tree</span></a><span class="plain-syntax">(), </span><span class="identifier-syntax">_p_</span><span class="plain-syntax">(</span><span class="identifier-syntax">PM_CantCompareValues</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><a href="14-lv.html#SP7" class="function-link"><span class="function-syntax">Lvalues::get_storage_form</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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="constant-syntax">PROPERTY_VALUE_NT</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="26-pc.html#SP7" class="function-link"><span class="function-syntax">Plugins::Call::forbid_setting</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-syntax">pt1</span><span class="plain-syntax">.</span><span class="identifier-syntax">term_checked_as_kind</span><span class="plain-syntax">)) {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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="named-paragraph-container code-font"><a href="12-ter.html#SP7_4" class="named-paragraph-link"><span class="named-paragraph">Make a further check that kinds permit this assignment</span><span class="named-paragraph-number">7.4</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="12-ter.html#SP7_5" class="named-paragraph-link"><span class="named-paragraph">Issue problem message for being unable to set equal</span><span class="named-paragraph-number">7.5</span></a></span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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="12-ter.html#SP7_3" class="named-paragraph-link"><span class="named-paragraph">Exceptional case of setting the "player" global variable</span><span class="named-paragraph-number">7.3</span></a></span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><a href="12-is.html#SP3_1" class="function-link"><span class="function-syntax">Calculus::Schemas::modify</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"%s"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><a href="14-lv.html#SP15" class="function-link"><span class="function-syntax">Lvalues::interpret_store</span></a><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="12-ter.html#SP7_6" class="named-paragraph-link"><span class="named-paragraph">Add kind-checking code for run-time checking</span><span class="named-paragraph-number">7.6</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="SP7_1" class="paragraph-anchor"></a><b>§7.1. </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">7.1</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">property</span><span class="plain-syntax"> *</span><span class="identifier-syntax">prn</span><span class="plain-syntax"> = </span><a href="15-cp.html#SP5" class="function-link"><span class="function-syntax">Properties::Conditions::get_coinciding_property</span></a><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><a href="12-is.html#SP3_1" class="function-link"><span class="function-syntax">Calculus::Schemas::modify</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"*1.%n == *2"</span><span class="plain-syntax">, </span><a href="15-pr.html#SP26" class="function-link"><span class="function-syntax">Properties::iname</span></a><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><a href="12-is.html#SP3_1" class="function-link"><span class="function-syntax">Calculus::Schemas::modify</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-syntax">schema</span><span class="plain-syntax">, </span><span class="string-syntax">"*1.%n = *2"</span><span class="plain-syntax">, </span><a href="15-pr.html#SP26" class="function-link"><span class="function-syntax">Properties::iname</span></a><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="12-ter.html#SP7">§7</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP7_2" class="paragraph-anchor"></a><b>§7.2. </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">7.2</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><a href="1-wtc.html#SP6" class="function-link"><span class="function-syntax">Task::syntax_tree</span></a><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><a href="12-is.html#SP3_1" class="function-link"><span class="function-syntax">Calculus::Schemas::modify</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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="12-ter.html#SP7">§7</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP7_3" class="paragraph-anchor"></a><b>§7.3. </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">7.3</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">nonlocal_variable</span><span class="plain-syntax"> *</span><span class="identifier-syntax">nlv</span><span class="plain-syntax"> =</span>
|
|
<span class="plain-syntax"> </span><a href="14-lv.html#SP8" class="function-link"><span class="function-syntax">Lvalues::get_nonlocal_variable_if_any</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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><a href="6-nv.html#SP21" class="function-link"><span class="function-syntax">NonlocalVariables::must_be_constant</span></a><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="element-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="reserved-syntax">char</span><span class="plain-syntax"> *</span><span class="identifier-syntax">exotica</span><span class="plain-syntax"> = </span><a href="6-nv.html#SP13" class="function-link"><span class="function-syntax">NonlocalVariables::get_write_schema</span></a><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><a href="12-is.html#SP3_1" class="function-link"><span class="function-syntax">Calculus::Schemas::modify</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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="12-ter.html#SP7">§7</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP7_4" class="paragraph-anchor"></a><b>§7.4. </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">7.4</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><a href="2-sq.html#SP3" class="function-link"><span class="function-syntax">Problems::quote_kind</span></a><span class="plain-syntax">(2, </span><span class="identifier-syntax">st</span><span class="plain-syntax">[1]);</span>
|
|
<span class="plain-syntax"> </span><a href="2-sq.html#SP3" class="function-link"><span class="function-syntax">Problems::quote_kind</span></a><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><a href="1-wtc.html#SP6" class="function-link"><span class="function-syntax">Task::syntax_tree</span></a><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="element-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="12-ter.html#SP7">§7</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP7_5" class="paragraph-anchor"></a><b>§7.5. </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">7.5</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><a href="14-rv.html#SP3" class="function-link"><span class="function-syntax">Rvalues::to_instance</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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><a href="14-sp.html#SP1" class="function-link"><span class="function-syntax">Specifications::to_kind</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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><a href="1-wtc.html#SP6" class="function-link"><span class="function-syntax">Task::syntax_tree</span></a><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>
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<span class="plain-syntax"> </span><span class="string-syntax">"can't alter matters."</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="identifier-syntax">StandardProblems::sentence_problem</span><span class="plain-syntax">(</span><a href="1-wtc.html#SP6" class="function-link"><span class="function-syntax">Task::syntax_tree</span></a><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>
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<span class="plain-syntax"> </span><span class="string-syntax">"I can't change that"</span><span class="plain-syntax">,</span>
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|
<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>
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|
<span class="plain-syntax"> </span><span class="string-syntax">"as values that vary. But others are fixed. If we write 'The "</span>
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|
<span class="plain-syntax"> </span><span class="string-syntax">"oak tree can be sturdy, lightning-struck or leaning.', for "</span>
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|
<span class="plain-syntax"> </span><span class="string-syntax">"instance, then 'sturdy' is a name for a value which is fixed, "</span>
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<span class="plain-syntax"> </span><span class="string-syntax">"just as the number '7' is fixed."</span><span class="plain-syntax">);</span>
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|
<span class="plain-syntax"> }</span>
|
|
</pre>
|
|
<ul class="endnotetexts"><li>This code is used in <a href="12-ter.html#SP7">§7</a>.</li></ul>
|
|
<p class="commentary firstcommentary"><a id="SP7_6" class="paragraph-anchor"></a><b>§7.6. </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">7.6</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">
|
|
<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>
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|
<span class="plain-syntax"> </span><a href="13-rsfk.html#SP3" class="function-link"><span class="function-syntax">Kinds::RunTime::I6_classname</span></a><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><a href="12-is.html#SP3_2" class="function-link"><span class="function-syntax">Calculus::Schemas::append</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">asch</span><span class="plain-syntax">-></span><span class="element-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="12-ter.html#SP7">§7</a>.</li></ul>
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|
<p class="commentary firstcommentary"><a id="SP8" class="paragraph-anchor"></a><b>§8. Problem message text. </b></p>
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<pre class="displayed-code all-displayed-code code-font">
|
|
<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">Calculus::Equality::REL_describe_for_problems</span><span class="plain-syntax">(</span><span class="identifier-syntax">OUTPUT_STREAM</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="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">FALSE</span><span class="plain-syntax">;</span>
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|
<span class="plain-syntax">}</span>
|
|
</pre>
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