#18411: get rid of CartesianProduct
-------------------------+-------------------------------------------------
Reporter: | Owner:
vdelecroix | Status: needs_work
Type: | Milestone: sage-6.7
enhancement | Resolution:
Priority: major | Merged in:
Component: | Reviewers:
combinatorics | Work issues:
Keywords: | Commit:
Authors: | 9f29074cb9a30ee194affe77ed5b7a28f9318df1
Vincent Delecroix | Stopgaps:
Report Upstream: N/A |
Branch: |
public/18411 |
Dependencies: |
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Comment (by vdelecroix):
I got into troubles. Combinatorial free modules are too laxist and you
discover mistakes only very lately... in the following an element `g` is
built
{{{
sage: M = SchurTensorModule(QQ, 2, 2)
sage: A = M._schur
sage: f = M.basis()[(1,1)]
sage: e = A.basis().values()[0]
sage: g = e*f
}}}
but it is not valid in the sense that the keys do not correspond to the
basis
{{{
sage: map(type, g.monomial_coefficients().keys())
[<type 'tuple'>]
sage: g.parent().basis().keys()
The cartesian product of ({1, 2}, {1, 2})
}}}
And hence you '''silently''' got
{{{
sage: g.to_vector()
(0, 0, 0, 0)
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/18411#comment:24>
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