>
> Bill: thank you for this useful work-around.
>
> Could someone please explain why the original conversion does not work?
>
In short: ATM it is unimplemented. Longer version: in Axiom
numerical evaluation was done as byproduct of conversion
to Expression(Float). More precisely, expression functions
try to perform evaluation in base ring and only if that
fails we get function in symbolic form. This design
has some problems:
- attempt at evaluation can change form of expression. Some
algorithms (like Risch algoritm) care about having specific
form and unpredictable change of form causes troubles
- evaluation may lead to spurious errors in case when
symbolic version is well defined, while version in
base ring is a partial function.
- each function which is subject to evaluation needs
several lines of boilerplate code
I am considering alternative apprach, having big switch in
'numeric' which dispatches to correct numeric function.
Current state is that functions which were present in
Axiom can be evaluated via numeric or coercion to
'Expression(Float)'. I am waiting for new mechanizm
before addeing other functions to 'numeric'.
--
Waldek Hebisch
[email protected]
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