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The Learning Brick Sorter • Masterpiece 2 103

efficient in this task. Can you improve the UpdateKnowledgeBase() routine to take max-
imum advantage from the feedback provided by the user?

NOTE

When updating the knowledge base with a new data that contradicts the infor-
mation previously stored, some cells need to be assigned to KB_UNKNOWN.

Another possible extension to the software is making it able to place more than a
single color in the same bin. For example, it could handle the case where you have five
different colors and three bins, and two pairs of colors share a common bin.This requires
that the knowledge base have more rows than columns, that is more ranges than bins.
However, changing the constants BINS and RANGES is not enough: you have to modify
the UpdateKnowledgeBase() routine, because the assumption that when a color is assigned
to a bin the others cannot use that bin is no more valid.
If you are a teacher and use this project for some classroom work, you can assign
some theoretical analysis of the algorithm. For example, you can ask them to discover
what’s the shortest sequence that makes the knowledge base complete in the luckiest case,
and what’s the longest sequence in the worst case.

Summary

As you discovered in the chapter, the apparently trivial brick sorting application offered
many arguments for discussion and investigation.
A few tricks we used can prove useful for other robots and other situations.The posi-
tion tracking system of my Learning Brick Sorter — built around a touch sensor and a
pulley — not only avoids the missed-counts problem which affect the rotation sensors,
but shows a general solution to emulate a rotation sensor when you don’t have one. We
have also seen a practical application of the well-known trick of connecting a light sensor
and a touch sensor together on the same input port, thus expanding the possibilities of
our RCX.
While developing the software, we have explored a few programming techniques. For
example, how to emulate a bi-dimensional array over a mono-dimensional one, and more
generally, how to write a solid program that can handle any possible situation and is easy
to understand and maintain. We also had a quick look at trivalent logic, something dif-
ferent from the more common Boolean logic based on the true/false values, but a pow-
erful tool when facing problems that contain some degree of indetermination.
More importantly, my Learning Brick Sorter lets you enter the world of machines
that learn.Although the software of the Learning Brick Sorter is very simple compared to
most actual AI programs, it nevertheless has merit and provides some insight that doesn’t
require the reader to have strong technical competence in this field already.