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Logtalk - Object oriented extension to Prolog
Release 2.28.2

Copyright (c) 1998-2006 Paulo Moura.  All Rights Reserved.
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To load this example and for sample queries, please see the SCRIPT file.

You will also need to load the following files in the library directory: 
events_loader, types_loader, metapredicates_loader, and hierarchies_loader.
Alternatively, you may load the library all_loader file to load all library 
entities.

This folder contains an example of representation and handling of
relations using events. We have instances of class brick and a binary
brick_stack relation between the bricks. Every time we move a brick, we
want the bricks on top of it to move along. If we break the stack by
moving a middle brick, we want to automatically destroy the
corresponding relation tuple.

It's instructive to use the event debugger in the Logtalk library (loader 
file debugging_loader.lgt) to better understand this example. Set spy points 
in all brick instances and then activate the debugger.