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< ul class = "crumbs" > < li > < a href = "../index.html" > Home< / a > < / li > < li > < a href = "../compiler.html" > Services< / a > < / li > < li > < a href = "index.html" > calculus< / a > < / li > < li > < a href = "index.html#3" > Chapter 3: Binary Predicates< / 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; and also its less noble sidekick, the "has" relation.< / p >
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< ul class = "toc" > < li > < a href = "3-ter.html#SP2" > § 2. Family< / a > < / li > < li > < a href = "3-ter.html#SP3" > § 3. Initial stock< / a > < / li > < li > < a href = "3-ter.html#SP4" > § 4. 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 > Equality is the only relation in its family; but in Inform, there will be other
relations besides "has" in the spatial family.
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< / p >
< pre class = "displayed-code all-displayed-code code-font" >
< span class = "reserved-syntax" > bp_family< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > equality_bp_family< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > NULL< / span > < span class = "plain-syntax" > ;< / span >
< span class = "reserved-syntax" > bp_family< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > spatial_bp_family< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > NULL< / span > < span class = "plain-syntax" > ;< / span >
< span class = "reserved-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 >
< span class = "reserved-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 >
< / pre >
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< p class = "commentary firstcommentary" > < a id = "SP2" class = "paragraph-anchor" > < / a > < b > § 2. Family. < / b > This is a minimal representation only, for when the calculus module is used
in a non-Inform context: whereas Inform adds other methods to the equality
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family to handle its typechecking in < a href = "../assertions-module/8-terr.html" class = "internal" > The Equality Relation Revisited (in assertions)< / a > .
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< / p >
< pre class = "displayed-code all-displayed-code code-font" >
< span class = "reserved-syntax" > void< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > Calculus::Equality::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" > Calculus::Equality::start< / span > < / span > :< br / > Calculus Module - < a href = "1-cm.html#SP3" > § 3< / 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" > equality_bp_family< / span > < span class = "plain-syntax" > = < / span > < a href = "3-bpf.html#SP1" class = "function-link" > < span class = "function-syntax" > BinaryPredicateFamilies::new< / 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 = "constant-syntax" > STOCK_BPF_MTID< / span > < span class = "plain-syntax" > ,< / span >
< span class = "plain-syntax" > < / span > < a href = "3-ter.html#SP3" class = "function-link" > < span class = "function-syntax" > Calculus::Equality::stock< / span > < / a > < span class = "plain-syntax" > );< / span >
< 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 = "constant-syntax" > DESCRIBE_FOR_PROBLEMS_BPF_MTID< / span > < span class = "plain-syntax" > ,< / span >
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< span class = "plain-syntax" > < / span > < a href = "3-ter.html#SP4" class = "function-link" > < span class = "function-syntax" > Calculus::Equality::describe_for_problems< / 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 = "constant-syntax" > DESCRIBE_FOR_INDEX_BPF_MTID< / span > < span class = "plain-syntax" > ,< / span >
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< span class = "plain-syntax" > < / span > < a href = "3-ter.html#SP4" class = "function-link" > < span class = "function-syntax" > Calculus::Equality::describe_for_index< / span > < / a > < span class = "plain-syntax" > );< / span >
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< span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > spatial_bp_family< / span > < span class = "plain-syntax" > = < / span > < a href = "3-bpf.html#SP1" class = "function-link" > < span class = "function-syntax" > BinaryPredicateFamilies::new< / 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" > METHOD_ADD< / span > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > spatial_bp_family< / span > < span class = "plain-syntax" > , < / span > < span class = "constant-syntax" > STOCK_BPF_MTID< / span > < span class = "plain-syntax" > ,< / span >
< span class = "plain-syntax" > < / span > < a href = "3-ter.html#SP3" class = "function-link" > < span class = "function-syntax" > Calculus::Equality::stock_spatial< / span > < / a > < span class = "plain-syntax" > );< / span >
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< span class = "plain-syntax" > #< / span > < span class = "identifier-syntax" > endif< / span >
< span class = "plain-syntax" > }< / span >
< / pre >
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< p class = "commentary firstcommentary" > < a id = "SP3" class = "paragraph-anchor" > < / a > < b > § 3. Initial stock. < / b > Note the unique one-off way in which equality is made.
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< / p >
< 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::stock< / 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" > Calculus::Equality::stock< / span > < / span > :< br / > < a href = "3-ter.html#SP2" > § 2< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-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" > n< / 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" > n< / span > < span class = "plain-syntax" > == < / span > < span class = "constant-syntax" > 1< / 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 > < a href = "3-bp.html#SP9" class = "function-link" > < span class = "function-syntax" > BinaryPredicates::make_equality< / span > < / a > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > equality_bp_family< / 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 = "identifier-syntax" > EQUALITY_RELATION_NAME< / span > < span class = "plain-syntax" > ));< / span >
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< span class = "plain-syntax" > < / span > < a href = "3-bp.html#SP8" class = "function-link" > < span class = "function-syntax" > BinaryPredicates::set_index_details< / span > < / a > < 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 = "plain-syntax" > }< / span >
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< span class = "reserved-syntax" > void< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > Calculus::Equality::stock_spatial< / 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" > Calculus::Equality::stock_spatial< / span > < / span > :< br / > < a href = "3-ter.html#SP2" > § 2< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-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" > n< / 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" > n< / span > < span class = "plain-syntax" > == < / span > < span class = "constant-syntax" > 1< / span > < span class = "plain-syntax" > ) {< / span >
< 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 > < a href = "3-bp.html#SP10" class = "function-link" > < span class = "function-syntax" > BinaryPredicates::make_pair< / span > < / a > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > spatial_bp_family< / span > < span class = "plain-syntax" > ,< / span >
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< span class = "plain-syntax" > < / span > < a href = "3-bptd.html#SP3" class = "function-link" > < span class = "function-syntax" > BPTerms::new_full< / span > < / a > < 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 >
< span class = "plain-syntax" > < / span > < a href = "3-bptd.html#SP2" class = "function-link" > < span class = "function-syntax" > BPTerms::new< / span > < / a > < 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 >
< 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 = "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 = "identifier-syntax" > POSSESSION_RELATION_NAME< / span > < span class = "plain-syntax" > ));< / 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. Problem message text. < / b > < / p >
< 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::describe_for_problems< / 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" > Calculus::Equality::describe_for_problems< / span > < / span > :< br / > < a href = "3-ter.html#SP2" > § 2< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > bp_family< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > self< / span > < span class = "plain-syntax" > , < / span > < span class = "identifier-syntax" > OUTPUT_STREAM< / span > < span class = "plain-syntax" > ,< / span >
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< span class = "plain-syntax" > < / span > < span class = "reserved-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 = "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 >
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< span class = "reserved-syntax" > void< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > Calculus::Equality::describe_for_index< / 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" > Calculus::Equality::describe_for_index< / span > < / span > :< br / > < a href = "3-ter.html#SP2" > § 2< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > bp_family< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > self< / span > < span class = "plain-syntax" > , < / span > < span class = "identifier-syntax" > OUTPUT_STREAM< / span > < span class = "plain-syntax" > ,< / span >
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< span class = "plain-syntax" > < / span > < span class = "reserved-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" > WRITE< / span > < span class = "plain-syntax" > (< / span > < span class = "string-syntax" > "equality"< / span > < span class = "plain-syntax" > );< / span >
< span class = "plain-syntax" > }< / span >
< / pre >
< nav role = "progress" > < div class = "progresscontainer" >
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< ul class = "progressbar" > < li class = "progressprev" > < a href = "3-bp.html" > ❮ < / a > < / li > < li class = "progresschapter" > < a href = "P-wtmd.html" > P< / a > < / li > < li class = "progresschapter" > < a href = "1-cm.html" > 1< / a > < / li > < li class = "progresschapter" > < a href = "2-up.html" > 2< / a > < / li > < li class = "progresscurrentchapter" > 3< / li > < li class = "progresssection" > < a href = "3-bpf.html" > bpf< / a > < / li > < li class = "progresssection" > < a href = "3-bptd.html" > bptd< / a > < / li > < li class = "progresssection" > < a href = "3-bp.html" > bp< / a > < / li > < li class = "progresscurrent" > ter< / li > < li class = "progresssection" > < a href = "3-cs.html" > cs< / a > < / li > < li class = "progresschapter" > < a href = "4-trm.html" > 4< / a > < / li > < li class = "progresschapter" > < a href = "5-sc.html" > 5< / a > < / li > < li class = "progressnext" > < a href = "3-cs.html" > ❯ < / a > < / li > < / ul > < / div >
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< / nav > <!-- End of weave -->
< / main >
< / body >
< / html >