#18264: make map_coefficients in modules_with_basis safer or more general
-------------------------------------+-------------------------------------
Reporter: mantepse | Owner:
Type: enhancement | Status: needs_work
Priority: minor | Milestone: sage-6.7
Component: algebra | Resolution:
Keywords: map_coefficients, | Merged in:
modules_with_basis, base_ring, | Reviewers:
check arguments | Work issues:
Authors: Martin Rubey | Commit:
Report Upstream: N/A | 3a7761e95b8ca8b83e08635828a3754d751fe918
Branch: | Stopgaps:
u/mantepse/make_map_coefficients_in_modules_with_basis_safer_or_more_general|
Dependencies: |
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Comment (by mantepse):
As it turns out, I get several failures when I insist on trying to coerce
to the base ring! (I pushed the nonworking branch, to get feedback.) For
example:
{{{
File "src/sage/combinat/ncsf_qsym/ncsf.py", line 3405, in
sage.combinat.ncsf_qsym.ncsf.NonCommutativeSymmetricFunctions.Psi
Failed example:
test_psi(2)
...
TypeError: no conversion of this rational to integer
}}}
The test which fails looks as follows:
{{{
sage: NCSF = NonCommutativeSymmetricFunctions(ZZ)
sage: R = NCSF.R()
sage: Psi = NCSF.Psi()
sage: n = 2; a = R.sum([(-1) ** i * R[[1]*i + [n-i]] for i in range(n)])
sage: Psi(a)
}}}
The expected output is `Psi[2]` (literally). The easy fix would be to add
the optional argument `coerce=False` to the calls of `sum_of_terms` in
`ncsf.py` everywhere, but I'm not sure whether this is what I should do -
because that would mean that the answer to the question in my previous
comment is "3".
Martin
--
Ticket URL: <http://trac.sagemath.org/ticket/18264#comment:13>
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