2002-05-28 12:35:10 +01:00
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=================================================================
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Logtalk - Object oriented extension to Prolog
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2002-12-31 16:16:47 +00:00
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Release 2.14.6
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2002-05-28 12:35:10 +01:00
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Copyright (c) 1998-2002 Paulo Moura. All Rights Reserved.
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=================================================================
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% Sending to descendant the message p/1, returns the definition in root:
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| ?- descendant::p(Value).
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Value = root
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yes
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% Asserting a local definition for p/1 in descendant overrides the inherited
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% definition:
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| ?- descendant::(assertz(p(descendant)), p(Value)).
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Value = descendant
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yes
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% If we retract the local definition, again the inherited definition form root
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% will be used:
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| ?- descendant::(retractall(p(_)), p(Value)).
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Value = root
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yes
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% class does not understand the message p1/1 (the predicate is declared only
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% for the class descendant instances):
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| ?- class::p1(X).
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error(existence_error(predicate_declaration, p1(_)), class::p1(_), user)
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% the same message is valid for the class instances:
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| ?- instance::p1(X).
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X = class
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yes
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% If we assert a clause for a new predicate, p2/1, in the class
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% (a side-effect being a dynamic declaration of the predicate):
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| ?- class::assertz(p2(class)).
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yes
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% the new predicate, like p1/1, is not available for the class:
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| ?- class::p2(Value).
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error(existence_error(predicate_declaration, p2(_)), class::p2(_), user)
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% but is available for the class instances, the same way as p1/1:
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| ?- instance::p2(X).
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X = class
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yes
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% Using a prototype, assert three new predicates (the method object_assert/0
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% asserts the predicate public_predicate/0 from outside the prototype; the
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% method self_assert/0 asserts the predicate protected_predicate/0 in self;
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% the method this_assert/0 asserts the predicate private_predicate/0 in this):
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| ?- prototype::(object_assert, self_assert, this_assert).
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yes
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% and check the resulting scope of each predicate:
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| ?- prototype::dynamic_predicates.
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public_predicate/0 - public
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protected_predicate/0 - protected
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private_predicate/0 - private
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yes
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