#18520: Matrix morphism addition ignores bases
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Reporter: rbeezer | Owner:
Type: defect | Status: new
Priority: minor | Milestone: sage-6.8
Component: linear | Keywords: matrix morphism sum addition
algebra | Authors:
Merged in: | Report Upstream: N/A
Reviewers: | Branch:
Work issues: | Dependencies:
Commit: |
Stopgaps: |
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When two module or vector space morphisms are added, the `matrix_morphism`
module simply adds their matrix representations, '''even if the
representations have wildly different bases.''' To wit,
`S, T, R` are all versions of the identity linear transformation, so `S+T,
S+R` should just be `2I`.
{{{
sage: u = vector([1,2])
sage: S = linear_transformation(QQ^2, QQ^2, [[1,0],[0,1]])
sage: T = linear_transformation(QQ^2, QQ^2, [[1,0],[0,1]])
sage: good = ((S+T)(u) == S(u) + T(u))
sage: B = [vector([0,1]), vector([1,0])]
sage: V = (QQ^2).subspace_with_basis(B)
sage: R = T.restrict_domain(V)
sage: bad = ((S+R)(u) == S(u) + R(u))
sage: ugly = (S+R).matrix()
sage: good, bad, ugly
(
[1 1]
True, False, [1 1]
)
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/18520>
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