#14485: Creation of a polynomial over QQbar
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Reporter: tmonteil | Owner: malb
Type: defect | Status: new
Priority: minor | Milestone: sage-6.1
Component: commutative algebra | Resolution:
Keywords: QQbar, polynomial | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Changes (by mmezzarobba):
* cc: burcin (added)
Comment:
I was going to report another problem caused by the bogus coercion from
`SR`:
{{{
sage: CC.has_coerce_map_from(QQbar)
True
sage: QQbar.has_coerce_map_from(SR)
True
sage: CC.has_coerce_map_from(SR)
False
}}}
So I'm all in favor of removing it, even if it breaks stuff that should
never have worked in the first place.
We might want to put (or actually put back?) a coercion in the other
direction, since symbolic expressions can embed elements of `QQbar`. But
`SR` has coerce maps from `RR`, `CC`, `RLF`, etc., which yield other
coercions from `QQbar` by composition. Can we consider that all these maps
are the same because they only differ in the "precision" of the result? Or
should all coercions from inexact rings to `QQbar` be removed? (Note that
the coercion from `QQ` to `SR` has exactly the same problem.)
--
Ticket URL: <http://trac.sagemath.org/ticket/14485#comment:6>
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