:- object(polygon,
instantiates(abstract_class),
specializes(shape)).
:- info([
author is 'Paulo Moura',
version is 1.1,
date is 2004/1/8,
comment is 'Generic polygon.']).
:- public(nsides/1).
:- mode(nsides(?integer), zero_or_one).
:- info(nsides/1, [
comment is 'Polygon number of sides.',
argnames is ['Number']]).
:- public(area/1).
:- mode(area(-float), zero_or_one).
:- info(area/1, [
comment is 'Polygon area.',
argnames is ['Area']]).
:- public(perimeter/1).
:- mode(perimeter(?atom), zero_or_one).
:- info(perimeter/1, [
comment is 'Polygon perimeter.',
argnames is ['Perimeter']]).
:- end_object.
