#11239: Incorrect coercion of polynomials over finite fields
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Reporter: johanbosman | Owner: robertwb
Type: defect | Status: needs_info
Priority: major | Milestone: sage-4.7.2
Component: coercion | Keywords: finite fields, polynomials,
coercion
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Comment(by SimonKing):
Replying to [comment:3 dkrenn]:
> One way to solve this problem would be to check whether the coefficients
of one polynomial rings can be converted (coerced) to the other...
I would strongly advice against the attempt to solve it on the level of
conversion.
I know that at least some classes of polynomial rings are still following
the old coercion model, and am preparing a patch that is supposed to fix
that. According to the new model, there should be a method
`_element_constructor_` that does the conversion, and a separate
`_coerce_map_from_`, that determines whether there is a coercion (not just
a conversion).
I think that it is ok to have that bogus conversion - as long as it is not
used as a coercion. One could, of course, try to throw an error when doing
a conversion in the case that there is no fixed embedding of the base
rings. However, testing it ''repeatedly'', that's to say testing it ''for
each individual polynomial to be converted'', sounds like a waste of
computation time to me.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11239#comment:4>
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