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Logtalk - Object oriented extension to Prolog
Release 2.21.0

Copyright (c) 1998-2004 Paulo Moura.  All Rights Reserved.
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% start by loading the example:

| ?- logtalk_load(loader).
...


% both cars provide the same interface, declared in the protocol
% that is implemented by the categories imported by each object:

| ?- sedan::current_predicate(P).

P = reference/1 ;
P = capacity/1 ;
P = cylinders/2 ;
P = horsepower_rpm/2 ;
P = bore_stroke/2 ;
P = fuel/1
yes


| ?- coupe::current_predicate(P).

P = reference/1 ;
P = capacity/1 ;
P = cylinders/2 ;
P = horsepower_rpm/2 ;
P = bore_stroke/2 ;
P = fuel/1 ;
yes


% the sedan engine properties are the ones defined in the corresponding 
% imported category (classic):

| ?- sedan::(reference(Name), cylinders(Cylinders), horsepower_rpm(HP, RPM)).

Name = 'M180.940'
Cylinders = 6
HP = 94
RPM = 4800 
yes


% the coupe engine properties are the ones defined in the corresponding 
% imported category (sport) plus the ones inherited from the top category 
% (classic) which are not overridden:

| ?- coupe::(reference(Name), cylinders(Cylinders), horsepower_rpm(HP, RPM)).

Name = 'M180.941'
Cylinders = 6
HP = 110
RPM = 5000 
yes