Ralf Hemmecke wrote:
> It just comes to my mind that it was
> also forbidden to create Fraction Fraction Integer. But that must be
> handled somewhere else as I don't see it near badDoubles in clammed.boot

Well, in clammed.boot we have:

  badDoubles := CONS($QuotientField, '(Complex Polynomial Expression))

and int setq.lisp:

(SETQ |$QuotientField| '|Fraction|)

so in fact Fraction is there.

> In fact, I don't see a big problem with creating Fraction(F) where F is
> already a field. In fact, we could even have something like
> 
> Fraction(F: IntegralDomain): FracCat ==
>   if F has Field then F else add ...
> 
> That would probably require that every field exports FracCat. I don't
> see at the moment whether this would be impossible or make too much
> trouble. It seem that it has come up before.
> 
> http://axiom-wiki.newsynthesis.org/263ContinuedFractionReturnsIncorrectTypes
> 
> Any idea whether we could allow double-Fraction, i.e. make it work properly?

Just try, Fraction code is supposed to be general. If it does not
work then it can be treated as a bug.  OTOH unlike Expression
doubling Fraction looks useless to me.

BTW: IIRC the real problem in 263 is that algorithm does not make much
sense for Fields.  I did not check if result is "correct" but clearly
what is computed is different from what user expect.  Here strange
type may be a hint for user that his/her expectations are not
satisfied.

-- 
                              Waldek Hebisch
[email protected] 

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