#11981: map_coefficients (of multivariate polynomial ring) cannot change
base_ring
---------------------------+------------------------------------------------
Reporter: dkrenn | Owner: AlexGhitza
Type: enhancement | Status: new
Priority: major | Milestone: sage-4.7.2
Component: algebra | Keywords: map coefficients, multivariate
polynomial ring, base ring
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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The `map_coefficients()` function of a multivariate polynomial ring cannot
change the base ring. Sometimes this would be nice, e.g.
{{{
sage: R.<r> = GF(9); S.<s> = GF(81)
sage: h = Hom(R,S)[0]; h
Ring morphism:
From: Finite Field in r of size 3^2
To: Finite Field in s of size 3^4
Defn: r |--> 2*s^3 + 2*s^2 + 1
sage: T.<X,Y> = R[]
sage: f = r*X+Y
sage: f.map_coefficients(h)
Traceback (most recent call last)
...
NotImplementedError:
}}}
`NotImplementedError` comes, because `R(2*s^3 + 2*s^2 + 1)` is not
possible; it should be `S(2*s^3 + 2*s^2 + 1)`.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11981>
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