[Axiom-developer] Re: CliffordPackage

[Bertfried Fauser]

Hi Martin,

my posts to fricas-devel are currently rejected by google, so I write
this also directly to you.

> These changes make good sense to me. I will just note for the record that they
> change the user interface and would therefore break any applications already
> using CliffordAlgebra but the changes are important enough to justify that.

Since the Clifford code was broken from the outset, the only place
where it actually shows up is the AXIOM book, which would then also
need an update,
I doubt threre is any other place (and I will see if I can chack that,
a grep over the code should do, I found CliffordAlgebra mentioned in

* browse.daase
* category.daase
* operation.daase
* compres.daase
* interp.daase
* exposed.lsp.pamphlet.svn-base
* clifford.spad.pamphlet
* abbrevs.input
* extract-spad.mk
* comdb.text
* libdb.text
* DEPENDENTS.DAASE
* CLIF.spad
* /USERS.DAASE/index.KA
* hyper/pages/.svn/text-base/CLIF.ht.svn-base
* hyper/pages/.svn/text-base/QUAT.ht.svn-base
* hyper/pages/QUAT.ht
* hyper/pages/QUAT2.ht
* hyper/pages/xmpexp.ht
* hyper/pages/ug02.ht
* hyper/pages/ug13.ht
* hyper/pages/CLIF.ht
* input/clifford.input.pamphlet
* paste/CLIF.input
* paste/CLIF.phts
* padhelp/Quaternion.help
* spadhelp/CliffordAlgebra.help
* topics.data
* command.list
)

I am not a grep expert, so things may have sliped through, otherwise I
think the above given list proves that CliffordAlgebra is not used by
any other package.

> OK, I will check if division or swapping of operands is done.

That was just a feature request, forget about noncommutytive rings at
the moment.

> the domain constructor as 'List List Ring', 'SquareMatrix Ring' or create a
> custom domain called BilinearForm ? Would I be correct in thinking that Matrix
> or a custom domain would not add much value so I might as well use a List of
> Lists for efficiency?

I would be happy with List List Ring, but since its a map between
vector spaces or modules, some popele on the list (if this mail gets
through) will have different oppinions. A square matrix could do, but
actually you only want to read out the elements, nothing else is done
with this array, so I would look (ask on teh list) what data structure
has the best random acess performance, List List is possibly slow, but
on the other hand such arrays will be in practice something like up to
10x10, so no hassle.

> Yes please, this would be very helpful, no rush though, as it will take me
> some time to absorb all this good information that you have given me.

OK, as soon as my maple is up again, I'll produce some test cases for you
(and we need to do AXIOM test cases for Tim ;-))

Ciao
BF.

-- 
% PD Dr Bertfried Fauser
%       Research Fellow, School of Computer Science, Univ. of Birmingham
%       Honorary Associate, University of Tasmania
%       Privat Docent: University of Konstanz, Physics Dept
<http://www.uni-konstanz.de>
% contact |->    URL : http://www.cs.bham.ac.uk/~fauserb/
%              Phone :  +44-121-41-42795 and +49 1520 9874517