/* Ellipses are defined by centre and semi-axes */
:- object(ellipse(_Center, _A, _B)).
:- info([
author is 'Paulo Moura',
version is 1.0,
date is 2000/4/22,
comment is 'Parametric object for representing geometric ellipses.',
parnames is ['Center', 'Rx', 'Ry'],
source is 'Example adopted from the POEM system by Ben Staveley-Taylor.']).
:- public(area/1).
:- mode(area(-number), one).
area(Area) :-
pi(Pi),
parameter(2, A),
parameter(3, B),
Area is Pi*A*B.
pi(3.14196).
:- end_object.
