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Re: [Axiom-developer] Unit package question

From: Ralf Hemmecke
Subject: Re: [Axiom-developer] Unit package question
Date: Tue, 23 Aug 2005 16:22:36 +0200
User-agent: Mozilla Thunderbird 1.0 (X11/20041206)

Hello Clifford,

(I should note that I don't use Aldor, just basic Axiom - I tend to
stick to open source stuff, so Aldor specific syntax won't be
terribly useful if it's too different from Axiom's.  Is Aldor's
syntax a subset of Axiom's?)

I would rather say that Axiom is the subset. The advantage with Aldor is
that it is a real programming language. You know, it developed from
Axiom and Peter Broadbery even seemed to have opened the stage for
programming extensions of Axioms Algebra library in Aldor (not SPAD).

Aldor is much clearer than SPAD. You will agree on that when you later
have to understand what you once have written in SPAD.

I think you should try to ask Stephen Watt, whether the Aldor compiler
will ever become open source. He claims that there is still some
copyright issues to be solved. But I don't know which. Maybe it helps if
many people ask him for opensourcing it. I would be very much in favour
of it. Peter Broadbery once worked with NAG on Aldor and I think he
could do wonderful things with making the Aldor compiler better. Anyway
at least he could document the code properly that he added to the
compiler. So I rather ask you to help making Aldor free.

Are Exports visible to the user on the command line or do they manifest themselves in the parent Category?

What is the parent Category here?

I guess I was thinking something like a Category Dimension and the various Domains (Mass, Length, etc.) as members of that Category. Sounds like that might not be the right way to work things though.

Right. The reason is: what do ALL dimension domains have in common? I
cannot think of a single function, except, maybe "convert".

OK. What about this - have two domains, Dimensions and Units. Have Units depend on Dimensions and define its units in terms of

He? Maybe I am missing the difference beteen dimensions and units. What
is what?

Is this allowed? This would separate things conceptually and would probably make things like dimensional analysis much simpler.

Ah, I've heard of dimensional analysis once. That rather checks whether
the type of the result has the correct format. Oh, that somehow seems to
suggest the domain way. But first explain. And maybe let me sleep then a
night about it.

Anyway, such a Metadomain would know about combinations of the basic domains and you have a Unit domain again which knows about all units.

Heh - good point :-).

Well, yes, but as far as I understand you want to distinguish the type
of the units (length, time, mass, etc.). So maybe the metadomain approach would be a good idea.


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