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Re: [Axiom-developer] Question concerning types...

From: Martin Rubey
Subject: Re: [Axiom-developer] Question concerning types...
Date: 17 Sep 2006 09:44:05 +0200
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3

Gabriel Dos Reis <address@hidden> writes:

> However, I seem to remember Ralf telling people that they should never
> ever enter EXPR T in Axiom; so without knowing what you do futher with
> your matrix I can't say the EXPR domain constructor is a good way to go;
> you have to try.

I think that one has to be more careful before judging EXPR that way. I'd
rather say: try to avoid EXPR as much as you can, but there are things which
cannot be handled without.

EXPR QUAT FRAC INT would be the domain of expressions, with coefficients (i.e.,
all "numbers" that appear) being from QUAT FRAC INT.

Internally (and that might be good for understanding), the elements are stored
as fractions of multivariate polynomials with coefficients being QUAT FRAC INT
and symbols being "kernels", i.e., things that cannot be evaluated further.

Cliff, maybe you would be happy with the domain


this one is "safer" - doesn't provide as much functionality though.

by the way, maybe it wasn't explained that way yet:

a: INT,; b: INT; a+b

+ is an operation in INT. it takes its arguments and applies the '+' function
from Lisp. The point is: +$INT was promised that the arguments it gets are
INTs. It's the design of axiom that every operation knows what types its
arguments have. They don't have to check anymore. That's why axiom is fast.

Go to a common lisp and say

(+ a b)


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