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|
=================================================================
Logtalk - Object oriented extension to Prolog
Release 2.27.1
Copyright (c) 1998-2006 Paulo Moura. All Rights Reserved.
=================================================================
% start by loading the example:
| ?- logtalk_load(dynpred(loader)).
...
% sending to descendant the message p/1, returns the definition in root:
| ?- descendant::p(Value).
Value = root
yes
% asserting a local definition for p/1 in descendant overrides the inherited
% definition:
| ?- descendant::(assertz(p(descendant)), p(Value)).
Value = descendant
yes
% if we retract the local definition, again the definition inherited from root
% will be used:
| ?- descendant::(retractall(p(_)), p(Value)).
Value = root
yes
% class does not understand the message p1/1 (the predicate is declared only
% for the class descendant instances):
| ?- class::p1(X).
error(existence_error(predicate_declaration, p1(_)), class::p1(_), user)
% the same message is valid for the class instances:
| ?- instance::p1(X).
X = class
yes
% if we assert a clause for a new predicate, p2/1, in the class
% (a side-effect being a dynamic declaration of the predicate):
| ?- class::assertz(p2(class)).
yes
% the new predicate, like p1/1, is not available for the class:
| ?- class::p2(Value).
error(existence_error(predicate_declaration, p2(_)), class::p2(_), user)
% but is available for the class instances, the same way as p1/1:
| ?- instance::p2(X).
X = class
yes
% using a prototype, assert three new predicates (the method object_assert/0
% asserts the predicate public_predicate/0 from outside the prototype; the
% method self_assert/0 asserts the predicate protected_predicate/0 in self;
% the method this_assert/0 asserts the predicate private_predicate/0 in this):
| ?- prototype::(object_assert, self_assert, this_assert).
yes
% and check the resulting scope of each predicate:
| ?- prototype::dynamic_predicates.
public_predicate/0 - public
protected_predicate/0 - protected
private_predicate/0 - private
yes
|
