#10349: Implementation of mutations for matrices
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Reporter: stumpc5 | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-4.7.1
Component: combinatorics | Keywords: matrix mutation
Work_issues: | Upstream: N/A
Reviewer: Hugh Thomas | Author: Christian Stump
Merged: | Dependencies: #10347
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Changes (by hthomas):
* cc: hthomas@… (added)
* reviewer: => Hugh Thomas
* status: needs_review => needs_work
Comment:
Hi Christian--
What do you think about the idea of checking that 0 <= k <
min(ncols,nrows)? Your code is very nicely written to be safe even if
someone tries to mutate a 2x2 matrix at row 15, but they shouldn't be
doing that. More importantly, they shouldn't be trying to mutate a 2n x n
matrix at row j for n<= j < 2n -- for such a parameter, mutation is
*undefined*. Returning what looks like meaningful output in such a case
is potentially deceptive. (That's my view, at any rate, though if you
disagree, I could be convinced otherwise.)
It's also true that the principal part of B should be skew-symmetrizable,
but I don't think it's necessary to check that -- though maybe it would be
good to mention this in the documentation? (The legit range of k values
should also go in the documentation, I guess.)
And, Zelevinsky :)
Otherwise, though, it looks good.
cheers,
Hugh
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10349#comment:6>
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