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.. rst-class:: align-right

built-in predicate

.. index:: pair: extends_object/2-3; Built-in predicate .. _predicates_extends_object_2_3:

extends_object/2-3

Description

::

extends_object(Prototype, Parent) extends_object(Prototype, Parent, Scope)

Enumerates, by backtracking, all pairs of objects such that the first one extends the second. The relation scope is represented by the atoms public, protected, and private.

Modes and number of proofs

::

extends_object(?object_identifier, ?object_identifier) - zero_or_more extends_object(?object_identifier, ?object_identifier, ?scope) - zero_or_more

Errors

| Prototype is neither a variable nor a valid object identifier: | type_error(object_identifier, Prototype) | Parent is neither a variable nor a valid object identifier: | type_error(object_identifier, Parent) | Scope is neither a variable nor an atom: | type_error(atom, Scope) | Scope is an atom but an invalid entity scope: | domain_error(scope, Scope)

Examples

::

% enumerate objects derived from the state_space prototype: | ?- extends_object(Object, state_space).

% enumerate objects publicly derived from the list prototype: | ?- extends_object(Object, list, public).

.. seealso::

:ref:predicates_current_object_1, :ref:predicates_instantiates_class_2_3, :ref:predicates_specializes_class_2_3