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Logtalk - Object oriented extension to Prolog
Release 2.18.0

Copyright (c) 1998-2004 Paulo Moura.  All Rights Reserved.
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To load all entities in this example compile and load the loader file:

| ?- logtalk_load(loader).

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

This is a very simple example of the use of events and monitors to make 
profilers for an application. It's easy to modify to make it do much more. 
For instance, most Prolog compilers give you access to data concerning space 
usage (stacks, heap, etc).

The example defines three objects:

	message_counter
		using events, this object allows us to count the messages sent to
		spied objects 
	
	stop_watch
		using events, this object simply prints the cpu time before and after 
		a message sent to a spied object

	timer
		this object implements a method that sends a message to an object a 
		specified number of times, returning the average execution time