#15428: Partitions to posets
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Reporter: darij | Owner:
Type: enhancement | Status:
Priority: major | needs_work
Component: combinatorics | Milestone: sage-5.13
Keywords: sage-combinat, partition, | Resolution:
poset | Merged in:
Authors: Darij Grinberg | Reviewers: Travis
Report Upstream: N/A | Scrimshaw
Branch: | Work issues:
Dependencies: #15350 | Commit:
| Stopgaps:
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Comment (by darij):
Replying to [comment:17 nthiery]:
> Thanks. Maybe you could use SE rather than NW as well in the
documentation when you explain what the poset is about.
Will do next time I'm editing the file; good point!
> > About the DRYness, what exactly would you factor out? What do you mean
by "indexing" rows and columns?
>
> Oh, now I see the misunderstanding; I thought the option was about the
> indexing of the cells, ... Which indeed was stupid (same poset). Never
> mind.
>
> To make your code DRY, you could build two lists horizontal_covers and
> vertical_covers, then, depending on the options, map a reverse on them:
> {{{
> if ...:
> horizontal_covers = [ (j,i) for (i,j) in horizontal_covers ]
> if ...:
> vertical_covers = [ (j,i) for (i,j) in vertical_covers ]
> }}}
Hmm. TBH I still don't understand you. How do you get anything from
reversal? I'm building up a dictionary, not a list of cover relations. The
(arguably toy) timing I have done shows the dictionary to be faster:
{{{
sage: %timeit Poset({1: [2,3], 2: [4,5], 5: [6,7,8]})
1000 loops, best of 3: 1.31 ms per loop
sage: %timeit Poset([[1,2],[1,3],[2,4],[2,5],[5,6],[5,7],[5,8]])
100 loops, best of 3: 1.9 ms per loop
}}}
> For consistency, I would tend to favor non boolean options like
> horiz="left" / "right" (we have a bunch of them e.g. in the Coxeter
> code). But I don't have great suggestions for the option names
> themselves.
Hmm. I thought you wanted to get rid of strings as arguments. I'm not
really convinced of replacing a 2-letter string by 2 multiletter strings
:/
--
Ticket URL: <http://trac.sagemath.org/ticket/15428#comment:18>
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