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polygons

In this example we have several types of polygons that can be concentric. This is represented by a concentric binary relation ensuring that whenever a polygon is moved towards a new position, all polygons likewise concentric are moved along with them.

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

%versions

Start by loading the example and the required library files:

logtalk_load(polygons(loader)).

First create four polygons and move each one to a different position:

triangle::new(t, [position-(4, 5)]).

<!-- true. -->

square::new(s, [position-(3, 2)]).

<!-- true. -->

pentagon::new(p, [position-(7, 1)]).

<!-- true. -->

hexagon::new(h, [position-(2, 4)]).

<!-- true. -->

Create two tuples of relation concentric:

concentric::add_tuple([t, s]).

<!-- true. -->

concentric::add_tuple([p, h]).

<!-- true. -->

Check results:

concentric::tuple(Tuple), write(Tuple), nl, fail; true.

<!-- [t,s] [p,h]

true. -->

t::position(Xt, Yt), s::position(Xs, Ys), p::position(Xp, Yp), h::position(Xh, Yh).

<!-- Xh = 7, Yh = 1, Xp = 7, Xs = 4, Xt = 4, Yp = 1, Ys = 5, Yt = 5. -->

after_event_registry::monitors(Ma).

<!-- Ma = [concentric]. -->

Move the triangle and the hexagon to new positions:

t::move(3, 3), h::move(8, 4).

<!-- true. -->

Check results:

concentric::tuple(Tuple), write(Tuple), nl, fail; true.

<!-- [t,s] [p,h]

true. -->

t::position(Xt, Yt), s::position(Xs, Ys), p::position(Xp, Yp), h::position(Xh, Yh).

<!-- Xh = 8, Yh = 4, Xp = 8, Xs = 3, Xt = 3, Yp = 4, Ys = 3, Yt = 3. -->

after_event_registry::monitors(Ma).

<!-- Ma = [concentric]. -->

Create another tuple of relation concentric:

concentric::add_tuple([t, p]).

<!-- true. -->

Move the pentagon to a new position:

p::move(2, 7).

<!-- true. -->

Check results:

concentric::tuple(Tuple), write(Tuple), nl, fail; true.

<!-- [t,s] [p,h] [t,p]

true. -->

t::position(Xt, Yt), s::position(Xs, Ys), p::position(Xp, Yp), h::position(Xh, Yh).

<!-- Xh = 2, Yh = 7, Xp = 2, Xs = 2, Xt = 2, Yp = 7, Ys = 7, Yt = 7. -->

List after event monitors:

after_event_registry::monitors(Monitors).

<!-- Monitors = [concentric]. -->

Clean up instances, tuples and monitors:

concentric::remove_all_tuples.

<!-- true. -->

triangle::delete(t).

<!-- true. -->

square::delete(s).

<!-- true. -->

pentagon::delete(p).

<!-- true. -->

hexagon::delete(h).

<!-- true. -->