#9787: lagrange_polynomial(algorithm='divided_difference') fails over finite
fields
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Reporter: mmezzarobba | Owner: AlexGhitza
Type: defect | Status: needs_review
Priority: minor | Milestone: sage-6.4
Component: algebra | Resolution:
Keywords: | Merged in:
Authors: Peter Bruin | Reviewers: Miguel Marco
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/pbruin/9787-lagrange_polynomial | 57f432cfe194c56c1b258a2d37046d67b15b82ab
Dependencies: | Stopgaps:
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Comment (by pbruin):
Replying to [comment:13 mmarco]:
> Well, if it is clearly stated that the result should be in R, conversion
should also be allowed, from my point of view.
Fair point, I'll change that and improve the documentation.
> I can see solid arguments for any of the possible choices: coerce to
R.basis(), convert to R.basis(), or extend for the common universe of
R.basis() and the input. My personal choice would be the last one, but as
long as it is clearly documented, i could live with any.
I still think that `R.lagrange_polynomial(...)` should return something in
`R`. In practice it should be easy to convert the input into the base
ring, unless the user made this ring too small for some reason. In that
case the user can easily enlarge the base ring.
> Another option would be to include a keyword (like 'extend', for
example) to control the behaviour in this aspect. That way you can have a
default functionality, but also another option for the user to choose.
Although, it seems a bit overkill for this.
This sounds like a reasonable option, but I do think it is a bit overkill,
so someone who really wants it can implement it.
--
Ticket URL: <http://trac.sagemath.org/ticket/9787#comment:14>
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