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:- object(rectangle(_width, _height, _position),
imports(private::assignvars)).
:- info([
version is 1.0,
author is 'Paulo Moura',
date is 2005/1/8,
comment is 'A simple implementation of a geometric rectangle using assignable variables and parametric objects.',
parnames is ['Width', 'Height', 'Position']]).
:- public(init/0).
:- mode(init, one).
:- info(init/0,
[comment is 'Initialize rectangle position.']).
:- public(area/1).
:- mode(area(-integer), one).
:- info(area/1,
[comment is 'Rectangle area.',
argnames is ['Area']]).
:- public(move/2).
:- mode(move(+integer, +integer), one).
:- info(move/2, [
comment is 'Moves a rectangle to a new position.',
argnames is ['X', 'Y']]).
:- public(position/2).
:- mode(position(?integer, ?integer), zero_or_one).
:- info(position/2, [
comment is 'Rectangle current position.',
argnames is ['X', 'Y']]).
init :-
parameter(3, Position),
::assignable(Position, (0, 0)).
area(Area) :-
parameter(1, Width),
parameter(2, Height),
Area is Width*Height.
move(X, Y) :-
parameter(3, Position),
::Position <= (X, Y).
position(X, Y) :-
parameter(3, Position),
::Position => (X, Y).
:- end_object.
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