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Re: [Axiom-developer] Value stack overflow bug

From: Ayal Pinkus
Subject: Re: [Axiom-developer] Value stack overflow bug
Date: Mon, 9 Jun 2003 13:11:16 +0200

It isn't the aldor expertise that is needed but a comprehensive
understanding of the algebra code. The past code is undocumented
(the future code, nopefully, will correct this). Axiom grew up
as a research tool and represented the bleeding edge of computational
math in various areas. I can read the aldor code but it is hard to
infer WHY some algorithms work. (This is true even in the interpreter.
There are 7 parsers. One is a "zipper" parser done by Bill Burge who
wrote a book on parsing. However, the zipper parser is post-book and
is undocumented both in code and in theory.) In order to understand
the challenge pick up a copy of a computer algebra algorithms book
and consider what it would take to either write the code from those
descriptions or write the descriptions given the axiom code. I hope
to see the "book" level of documentation for Axiom. As part of that
effort it would make sense to rewrite the Axiom code in Aldor.

I think it is great that Axiom is striving to document the algorithms
used. That is in part what people are interested in. They would want
to know how it works, but also be able to use the algorithms.

I have had a look at Maxima, largely undocumented terse code.
Computer algebra algorithms are far from trivial. They are not
the kinds of algorithms where you can just look at the code and
figure out what is going on. I'd imagine the "zipper" code you mention
is another beast; parsers are not very complex, but it might be
highly optimized code, which becomes unreadable again (?)
For a system to become maintainable documentation is needed
very much. Ideally, the next generation needs to be able to pick
the system up and maintain it.

Yacas has a similar aim, documenting algorithms that can be
used for CAS purposes. I hope we can collaborate on this
maybe, somehow, by sharing information. I think no one wants
to abandon their project they have already put so much effort
in, but sharing information could benefit everybody.

On a side note, it is a bit intimidating to see a CAS that has been
30 years in development become available ;-) But there is
room for different systems, even if only so users of the systems
can verify their calculations by using different systems.
And strengths between the systems probably differ.

Another question, perhaps a bit of a newbie question: is
the code available through cvs? I tried to find it but to no
avail. (Tenkan? Maybe its cvs server was down when i tried).
Is it top secret? It would be just out of curiosity.

Ayal Pinkus

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