#17053: Add function for disjoint union and ordinal sum of posets
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Reporter: jmantysalo | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-wishlist
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jmantysalo/add_function_for_direct_sum_of_posets|
4b35a5413d0d18e075783484ff8079034e828d51
Dependencies: | Stopgaps:
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Comment (by jmantysalo):
Replying to [comment:27 ncohen]:
> > 7) Which one is logical for A.ordinal_sum(B): to have "A up and B
down" or "B up"? I don't know.
>
> This I do not know. But I would have expected the set of points `(1,x)`
to be greater than the ones labelled with `(0,x)`
You are right on that. On the other hand, somehow for `A.something(B)` it
sounds natural to have `(0,x)` be element of A and `(1,y)` be element of
B. From that I can deduce that `A.ordinal_sum(B)` should have elements of
B of on "up" and elements of A on "down".
> > 8) I'm quite sure about that. But how?
>
> Ask the guy in your office (if any) to read it, and if not I will do it
before setting the branch to `positive_review`.
Done this. I'll continue when he replies.
--
Ticket URL: <http://trac.sagemath.org/ticket/17053#comment:28>
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