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73 lines
2.2 KiB
OpenEdge ABL
73 lines
2.2 KiB
OpenEdge ABL
[Calculus::Equality::] The Equality Relation.
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To define that prince among predicates, the equality relation; and also its
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less noble sidekick, the "has" relation.
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@ Equality is the only relation in its family; but in Inform, there will be other
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relations besides "has" in the spatial family.
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= (early code)
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bp_family *equality_bp_family = NULL;
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bp_family *spatial_bp_family = NULL;
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binary_predicate *R_equality = NULL;
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binary_predicate *a_has_b_predicate = NULL;
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@h Family.
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This is a minimal representation only, for when the calculus module is used
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in a non-Inform context: whereas Inform adds other methods to the equality
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family to handle its typechecking in //assertions: The Equality Relation Revisited//.
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=
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void Calculus::Equality::start(void) {
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equality_bp_family = BinaryPredicateFamilies::new();
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METHOD_ADD(equality_bp_family, STOCK_BPF_MTID,
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Calculus::Equality::stock);
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METHOD_ADD(equality_bp_family, DESCRIBE_FOR_PROBLEMS_BPF_MTID,
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Calculus::Equality::describe_for_problems);
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METHOD_ADD(equality_bp_family, DESCRIBE_FOR_INDEX_BPF_MTID,
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Calculus::Equality::describe_for_index);
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spatial_bp_family = BinaryPredicateFamilies::new();
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#ifndef IF_MODULE
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METHOD_ADD(spatial_bp_family, STOCK_BPF_MTID,
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Calculus::Equality::stock_spatial);
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#endif
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}
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@h Initial stock.
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Note the unique one-off way in which equality is made.
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=
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void Calculus::Equality::stock(bp_family *self, int n) {
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if (n == 1) {
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R_equality = BinaryPredicates::make_equality(equality_bp_family,
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PreformUtilities::wording(<relation-names>, EQUALITY_RELATION_NAME));
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BinaryPredicates::set_index_details(R_equality, "value", "value");
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}
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}
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void Calculus::Equality::stock_spatial(bp_family *self, int n) {
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if (n == 1) {
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a_has_b_predicate =
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BinaryPredicates::make_pair(spatial_bp_family,
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BPTerms::new_full(NULL, NULL, EMPTY_WORDING, NULL),
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BPTerms::new(NULL),
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I"has", I"is-had-by",
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NULL, NULL,
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PreformUtilities::wording(<relation-names>, POSSESSION_RELATION_NAME));
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}
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}
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@h Problem message text.
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=
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int Calculus::Equality::describe_for_problems(bp_family *self, OUTPUT_STREAM,
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binary_predicate *bp) {
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return FALSE;
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}
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void Calculus::Equality::describe_for_index(bp_family *self, OUTPUT_STREAM,
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binary_predicate *bp) {
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WRITE("equality");
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}
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