#14789: Implement hyperplane arrangements
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Reporter: kcrisman | Owner: sage-combinat
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.12
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by kcrisman):
> I think the original comment was that it is a little odd that you can
have `a==b` return True while `a.sign_vector((2, -2))` returns something
different from `b.sign_vector((2, -2))`. If they are really sets of
hyperplanes, then the order in which those hyperplanes are specified
should have no impact. So are they sets, or are they lists?
+1 to the question
However, in this case maybe (maybe) it's okay. Because the question is
about "which side of the hyperplane the point is on" and that of course
requires an orientation to each hyperplane, given by the equation, and
naturally this list will depend on the order. However, the documentation
probably should include this example to point out that it definitely
depends on the order you give the hyperplanes in, just in case some
unsuspecting user might think otherwise. A sign set probably wouldn't be
of very much use.
By the way, I assume that we don't get
{{{
a is b
True
}}}
which I think ''would'' be a bug.
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Ticket URL: <http://trac.sagemath.org/ticket/14789#comment:27>
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