Opened 5 years ago

Closed 5 years ago

#21338 closed enhancement (fixed)

implement the poset of intervals of a poset

Reported by: chapoton Owned by:
Priority: minor Milestone: sage-7.4
Component: combinatorics Keywords:
Cc: jmantysalo Merged in:
Authors: Frédéric Chapoton Reviewers: Jori Mäntysalo
Report Upstream: N/A Work issues:
Branch: 966bfd4 (Commits, GitHub, GitLab) Commit: 966bfd4bbf3c7d9e17e29357954e729c18cba7a5
Dependencies: Stopgaps:

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Description

this is a useful construction to have

Change History (12)

comment:1 Changed 5 years ago by chapoton

  • Branch set to u/chapoton/21338
  • Commit set to d40082a97896c42962ef9cb751d38ce0abb4ae28

New commits:

d40082aimplement the poset of intervals of a poset

comment:2 Changed 5 years ago by jmantysalo

Good idea.

  • I think that this needs seealso-crosslinks with sublattices_lattice().
  • Should return type be lattice when self is of type lattice? Compare for example to dual().
  • We really should have a guideline whether to use self or "the thing" at docstrings. This now conflicts with other functions at posets.py.

comment:3 Changed 5 years ago by git

  • Commit changed from d40082a97896c42962ef9cb751d38ce0abb4ae28 to da1e421718e66624a3d78a5b9c3681e20f4c8697

Branch pushed to git repo; I updated commit sha1. New commits:

da1e421trac 21338 more work on posets of intervals

comment:4 Changed 5 years ago by git

  • Commit changed from da1e421718e66624a3d78a5b9c3681e20f4c8697 to 9edc8601a3f7ea297812be2e575dabe118310d60

Branch pushed to git repo; I updated commit sha1. New commits:

9edc860trac 21338 more work, not successful

comment:5 Changed 5 years ago by git

  • Commit changed from 9edc8601a3f7ea297812be2e575dabe118310d60 to 089493916d1b3a518ffb678a5b8197236710f381

Branch pushed to git repo; I updated commit sha1. New commits:

0894939trac 21338 ready for review

comment:6 Changed 5 years ago by chapoton

  • Status changed from new to needs_review

ok, ready for review now

comment:7 Changed 5 years ago by jmantysalo

Tests passed, nothing wrong with the code etc. The function does what it says to do, so I could put this to positive review. And the code is fast -- good work!

But where is this "natural partial order" defined? I would have guessed from the name that it means a poset where [a,b] <= [c,d] iff a >= c and b <= d. Then for lattices it would be lattice of convex sublattices, hence a sublattice of lattice of (all) sublattices. That's why I suggested seealso-crosslinks; sorry for not reading this carefully.

comment:8 follow-up: Changed 5 years ago by chapoton

This is natural in the following sense:

a poset is a category, a morphism of posets is a functor, a morphism between morphisms of posets is a natural transformation.

So if posets are understood in the proper language, there is no real choice for a natural definition of a partial order on the morphisms from 2 to P.

Should I remove the cross-links ?

comment:9 in reply to: ↑ 8 Changed 5 years ago by jmantysalo

  • Reviewers set to Jori Mäntysalo

Replying to chapoton:

Explanation accepted.

Should I remove the cross-links ?

Yes, I guess so. After that you can click positive_review on behalf of me.

comment:10 Changed 5 years ago by git

  • Commit changed from 089493916d1b3a518ffb678a5b8197236710f381 to 966bfd4bbf3c7d9e17e29357954e729c18cba7a5

Branch pushed to git repo; I updated commit sha1. New commits:

e09a7cbMerge branch 'u/chapoton/21338' in 7.4.b2
966bfd4trac 21338 removing seealsos

comment:11 Changed 5 years ago by chapoton

  • Status changed from needs_review to positive_review

done, thanks. Setting to positive

comment:12 Changed 5 years ago by vbraun

  • Branch changed from u/chapoton/21338 to 966bfd4bbf3c7d9e17e29357954e729c18cba7a5
  • Resolution set to fixed
  • Status changed from positive_review to closed
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