Prof. Dr. Johannes Grabmeier wrote:
>
> Ok, this is very unimportant problem, nevertheless one could think about co=
> ercion principles.
>
> The bad guy is ScanRoman, but the strange thing is, that in order to find a=
> - for a variable x and a number 4, AXIOM/FriCAS rather looks for a routine=
> to coerce the variable to a number and not - as I would expect here - to g=
> o to Polynomials.
>
> Hence, one really has to work very hard to get a polynomial over the RomanN=
> umerals.
>
AXIOM/FriCAS coercion system is type based. Both 'a' and 'x' are
quickly coeced to Symbol and then are handled in the same way.
If we want coercion of 'x' to 10 in ROMAN, then it is hard to
avoid attempts to do similar coercion for 'a'. Of course, we
could add enough backtracking so that after attempt to coerce
to ROMAN we would try to coerce to Polynomial. However, such
backtracking in general is very expensive and gives unpredictable
results, so interpreter frequently commits to a single choice
and when this choice fails it declares a failure.
--
Waldek Hebisch
[email protected]
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