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This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 1998-2023 Paulo Moura <pmoura@logtalk.org> SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

% start by loading the example and the required library files:

| ?- logtalk_load(blocks(loader)). ...

% create four blocks, all standing on the "ground" (use your imagination... ;-) % (don't use message broadcasting syntax in order to workaround a XSB parser bug)

| ?- block::new(a, [position-(8, 1)]), block::new(b, [position-(6, 1)]), block::new(c, [position-(4, 1)]), block::new(d, [position-(2, 1)]). yes

% set up ascii stack monitor so we can watch the blocks moving

| ?- define_events(after, _, move(_,_), _, stack_monitor). yes

% ensure that top-level message goals generate events

| ?- set_logtalk_flag(events, allow). yes

% make the stack (don't use message broadcasting syntax in order to workaround a XSB parser bug)

| ?- block_stack::add_tuple(c-d), block_stack::add_tuple(b-c), block_stack::add_tuple(a-b). |.c...... |.d...b.a --------- |.b...... |.c...... |.d.....a --------- |.a |.b |.c |.d --- yes

% check results

| ?- block_stack::tuples(Tuples). Tuples = [c-d, b-c, a-b] yes

| ?- current_event(after, Object, Message, Sender, Monitor). Message = move(_, _), Monitor = stack_monitor ;

Object = d, Message = move(_, _), Monitor = block_stack ;

Object = c, Message = move(_, _), Monitor = block_stack ;

Object = a, Message = move(_, _), Monitor = block_stack ;

Object = b, Message = move(_, _), Monitor = block_stack yes

% move all stack to new position by moving bottom block; check results

| ?- d::move(9, 1). |.a....... |.b....... |.c....... |........d ---------- |.a....... |.b....... |........c |........d ---------- |.a....... |........b |........c |........d ---------- |........a |........b |........c |........d ---------- yes

| ?- a::position(Xa, Ya), b::position(Xb, Yb), c::position(Xc, Yc), d::position(Xd, Yd). Xa = 9, Xb = 9, Xc = 9, Xd = 9, Ya = 4, Yb = 3, Yc = 2, Yd = 1 yes

| ?- block_stack::tuples(Tuples). Tuples = [c-d, b-c, a-b] yes

% break stack in half by moving b to the "ground"; check results

| ?- b::move(3, 1). |........a |......... |........c |..b.....d ---------- |..a.....c |..b.....d ---------- yes

| ?- a::position(Xa, Ya), b::position(Xb, Yb), c::position(Xc, Yc), d::position(Xd, Yd). Xa = 3, Xb = 3, Xc = 9, Xd = 9, Ya = 2, Yb = 1, Yc = 2, Yd = 1 yes

| ?- block_stack::tuples(Tuples). Tuples = [c-d, a-b] yes

% create new block_stack tuple; check results

| ?- block_stack::add_tuple(d-a). |..d...... |..a.....c |..b...... ---------- |..c |..d |..a |..b ---- yes

| ?- a::position(Xa, Ya), b::position(Xb, Yb), c::position(Xc, Yc), d::position(Xd, Yd). Xa = 3, Xb = 3, Xc = 3, Xd = 3, Ya = 2, Yb = 1, Yc = 4, Yd = 3 yes

| ?- block_stack::tuples(Tuples). Tuples = [c-d, a-b, d-a] yes

% move all stack to new position by moving bottom block; check results

| ?- b::move(5, 1). |..c.. |..d.. |..a.. |....b ------ |..c.. |..d.. |....a |....b ------ |..c.. |....d |....a |....b ------ |....c |....d |....a |....b ------ yes

| ?- a::position(Xa, Ya), b::position(Xb, Yb), c::position(Xc, Yc), d::position(Xd, Yd). Xa = 5, Xb = 5, Xc = 5, Xd = 5, Ya = 2, Yb = 1, Yc = 4, Yd = 3 yes

| ?- block_stack::tuples(Tuples). Tuples = [c-d, a-b, d-a] yes

% clean up instances, tuples and monitors

| ?- block_stack::remove_all_tuples. yes

| ?- block::delete_all. yes