#18645: Add some methods to CartanMatrix
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Reporter: jonathan.judge | Owner: jonathan.judge
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.8
Component: combinatorics | Resolution:
Keywords: days65 | Merged in:
Authors: | Reviewers: Ben Salisbury
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jonathan.judge/add_some_methods_to_cartanmatrix|
8d06af9a2013822895f945e37cf7df0137b421ed
Dependencies: | Stopgaps:
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Comment (by tscrim):
A couple of things:
- IMO `not self.det() == 0` would be better as `self.det() != 0`.
- Instead of `return len([x for x in self.eigenvalues() if x < 0]) == 1`,
I would use `sum(1 for x in M.eigenvalues() if x < 0)` since then we don't
create the intermediate list (but this probably isn't really important
since matrices we consider are usually "small").
- I would do this import `from sage.misc.misc import powerset` at the
module level. It makes the code run faster. (Sorry, I should have
mentioned this earlier.)
- I would cache the `is_*` methods since they actually seem to get called
with some frequency (specifically `is_finite`).
- I think your check for `is_hyperbolic` is overkill. You should instead
iterate over the vertices and check the subgraph of everything except that
vertex.
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Ticket URL: <http://trac.sagemath.org/ticket/18645#comment:15>
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