#19659: Poset: inverse function of ordinal_sum()
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Reporter: jmantysalo | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-7.0
Component: combinatorics | Resolution:
Keywords: poset | Merged in:
Authors: Jori Mäntysalo | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jmantysalo/develop | 4358a5a4574999015ccb9088bdb842dcc738d40c
Dependencies: | Stopgaps:
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Comment (by jmantysalo):
Replying to [comment:14 ncohen]:
> > This is true. But then, what's wrong with having functions at
`hasse_diagram.py`?
>
> I don't believe that a designs that requires you to implement two
functions every time you need one is a good thing.. Additionally, the
docstring of the !HasseDiagram function that currently appears in this
branch starts with `Return the ordinal decomposition of the poset`. This
method screams that it does not belong there.
Hasse diagram is a poset with some constraints... I can change that
docstring.
But the question remains: What is the meaning of `hasse_diagram.py`? Whole
poset class could be implemented with just a digraph as one member
variable. But then I guess we would have more internal functions starting
with `_`. Or more functions returning something actually only useful for
internal use.
An example: check (broken!) parameter `partial` at `maximal_chains`. It is
needed for `order_complex`. I think that the whole concept of "partial
maximal chain" is odd and should be removed. It could have placed in
`hasse_diagrams.py`, which is meant for internal implementation. (Btw, see
#18944 - my suggestion to drop `partial`-option was rejected.)
I think that I can generate something like all posets of size 7 in the
same time as all Hasse diagrams of size 8. So it really loses some cpu
time to make posets.
--
Ticket URL: <http://trac.sagemath.org/ticket/19659#comment:15>
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