#14485: Creation of a polynomial over QQbar
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Reporter: tmonteil | Owner: malb
Type: defect | Status: new
Priority: major | Milestone: sage-5.10
Component: commutative algebra | Resolution:
Keywords: QQbar, polynomial | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by nbruin):
The thing that goes wrong is the following:
{{{
sage: S=QQbar['x']
sage: S.base_ring().has_coerce_map_from(SR)
True
}}}
Once this is found, it's clear how an element of `SR` should be converted
into `QQbar['x']`: `SR` already coerces into `QQbar` itself, so we should
just convert the element into a "constant polynomial".
Except, of course, that `SR` doesn't really coerce into `QQbar`: Only
"constant" expressions might (and even then, of course `pi` doesn't), and
`x` of course isn't one of those. So the proper solution is probably to
NOT install a coercion from SR to QQbar, because it isn't a coercion
anyway. It's only a partial map. Doing so is probably going to be painful
for something else.
This problem doesn't arise for `AA` because it's pretty clear that not
even algebraic elements fit in `AA`, so no coercion is installed.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14485#comment:3>
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