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)]
     ).