#8992: Coercion of univariate quotient polynomial rings
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Reporter: SimonKing | Owner:
robertwb
Type: defect | Status:
needs_work
Priority: major | Milestone:
sage-5.0
Component: coercion | Keywords:
coercion quotient ring
Work_issues: rewrite, make polynomial division work | Upstream: N/A
Reviewer: PatchBot | Author: Simon
King
Merged: | Dependencies:
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Comment(by SimonKing):
The reason for my complaint about `y.divides(y)` is that the following
example from a comment above would not work with the patch that I am now
preparing:
{{{
sage: P.<x> = QQ[]
sage: Q1 = P.quo([(x^2+1)^2*(x^2-3)])
sage: R.<y> = P[]
sage: Q3 = R.quo([(y^2+1)]); Q3
Univariate Quotient Polynomial Ring in ybar over Univariate Polynomial
Ring in x over Rational Field with modulus y^2 + 1
sage: Q3(Q1.gen()) # uses the lift from Q1 to P, which is the base ring
of Q3
x
}}}
The problem is that the coercion framework is not able to find out whether
`Q3` has a coerce map from `Q1`.
So, I guess I should add a "try-except" clause in `Q3._coerce_map_from_`,
so that an error in division is caught and results in the answer "no,
there is no coerce map".
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8992#comment:9>
Sage <http://www.sagemath.org>
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