#12848: Bug in order_ideal_complement_generators: 'down'
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Reporter: nthiery | Owner:
sage-combinat
Type: defect | Status:
needs_review
Priority: major | Milestone:
sage-5.10
Component: combinatorics | Resolution:
Keywords: posets | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Nicolas M. Thiéry, Frédéric Chapoton | Merged in:
Dependencies: | Stopgaps:
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Comment (by nthiery):
Hi Frederic.
I agree that this naming thing is a pain; which is actually what
stopped me from cleaning this earlier. Thanks for pushing it forward ...
order_ideal and order_filter are definitely bad for the reason you
mention (which one is up, which one is down). So at least this is
settled: we want to move away from those.
upper_set and lower_set has the advantage of being unambiguous and
relatively clear (though I see your point about "closures"). So I
would vote for this. But ... we also would want to be able to pass
upper/lower as argument, and I agree that ``set(dir="up")`` really
does not make sense :-) And ``upper_set(dir='down') is not great
either.
I am really not keen with "ideal" because it has two conflicting
meanings. But it's been in Sage for a while and we already do
ideal(side="left/right") in rings/monoids, so ideal(dir="up/down") is
consistent.
Would we have a nice method name for the other definition of ideal
(e.g. a upper set such that any meet of two elements is also in it)?
Cheers,
Nicolas
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12848#comment:16>
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