[Axiom-developer] [#263 ContinuedFraction returns incorrect types] Re: Fraction R returns R when R is a field

[kratt6]

Changes 
http://wiki.axiom-developer.org/263ContinuedFractionReturnsIncorrectTypes/diff
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Thinking about it, I realized that this is not the proper solution, since 
'Fraction R' provides some operations, for example 'denominator' which 'R' does 
not necessarily have and I think it would be wrong to equip every 'Field' with 
this operation, which would then be necessary. Thus, either

-  Axiom's interpreter should not complain about types like 'Fraction Float'. 
In this case, 'denominator' will always return '1', of course. Note that you 
can perfectly well calculate with objects of type 'Stream Fraction Fraction 
Integer', no problem occurs. Or

- operations that want to return Fraction R have to check whether R is a field.

The code that excludes constructions like 'FRAC FRAC' and 'FRAC R' when 'R' is 
a field is in 'clammed.boot.pamphlet', lines 108-112.

Possibly we want to allow 'Fraction Field' but disallow 'Fraction Fraction'?

Martin
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