create_category/4¶
Description¶
create_category(Identifier, Relations, Directives, Clauses)
Creates a new, dynamic category. This predicate is often used as a primitive to implement high-level category creation methods.
Note that, when opting for runtime generated category identifiers, it’s possible to run out of identifiers when using a backend Prolog compiler with bounded integer support. The portable solution, when creating a large number of dynamic category in long-running applications, is to recycle, whenever possible, the identifiers.
When using Logtalk multi-threading features, predicates calling this built-in predicate may need to be declared synchronized in order to avoid race conditions.
Modes and number of proofs¶
create_category(?category_identifier, @list(category_relation), @list(category_directive), @list(clause)) - one
Errors¶
Relations, Directives, or Clauses is a variable:
instantiation_error
Identifier is neither a variable nor a valid category identifier:
type_error(category_identifier, Identifier)
Identifier is already in use:
permission_error(modify, category, Identifier)
permission_error(modify, object, Identifier)
permission_error(modify, protocol, Identifier)
Relations is neither a variable nor a proper list:
type_error(list, Relations)
Repeated entity relation clause:
permission_error(repeat, entity_relation, implements/1)
permission_error(repeat, entity_relation, extends/1)
permission_error(repeat, entity_relation, complements/1)
Directives is neither a variable nor a proper list:
type_error(list, Directives)
Clauses is neither a variable nor a proper list:
type_error(list, Clauses)
Examples¶
| ?- create_category(
tolerances,
[implements(comparing)],
[],
[epsilon(1e-15), (equal(X, Y) :- epsilon(E), abs(X-Y) =< E)]
).