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## [Axiom-developer] [Axiom-mail] Type of Expression Problem

 From: Hans Peter Würmli Subject: [Axiom-developer] [Axiom-mail] Type of Expression Problem Date: Sun, 13 Nov 2005 08:06:04 -0600

```Changes http://page.axiom-developer.org/zope/mathaction/AxiomMail/diff
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Dear Martin

> > but how then would you assert that something is in a Domain? I tried
> >
> > typeOf(3)=Integer
> >
> > but such a simple solution doesn't work.
>
> You got a quite tricky question there, really. If you are doing something
> else then trying to understand how axiom is doing things, it's very likely
> that you are on the wrong track. What are you trying to accomplish?

I might very well be on the wrong track. On one hand I am not really trying to
accomplish anything, but to understand Axiom, or, in fact, Axiom's
interpreter. On the other hand I usually try to solve some problem for such
exercises and I had thought that the summation algorithms a la Gosper are
quite useful for that. But even checking that some summand is a
hypergeometric term causes the greatest pain. So in fact, the last thing I
tried was trying to check wether a quotient

F(n-1,k)/F(n,k) ,

primarily given by an Expression Integer could be "coerced" / "converted" /
"retracted" (certainly not) to, say, a

Fraction Polynomial Integer.

Ideally, I would have used parsing operators and analysed such an expression
from scratch, but I lacked the proper clues to do that. Even though
Expressions are described someplace as "recursive", I haven't encountered the
representation and tools to use that fact, but that said I might not have
studied enough the "FunctionSpace"s.

I will answer your question in the other mail later. I need to travel today,
i.e. leave for the airport right now, and will only return late on Monday
night.

Thanks and best regards

H.P.

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