built-in predicate
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 creating a new dynamic parametric category, access to the object parameters must use the parameter/2 built-in execution context method.
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_errorIdentifier 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)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)]
).