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:  sage7.4 
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: 
Description
this is a useful construction to have
Change History (12)
comment:1 Changed 5 years ago by
 Branch set to u/chapoton/21338
 Commit set to d40082a97896c42962ef9cb751d38ce0abb4ae28
comment:2 Changed 5 years ago by
Good idea.
 I think that this needs seealsocrosslinks with
sublattices_lattice()
.  Should return type be lattice when
self
is of type lattice? Compare for example todual()
.  We really should have a guideline whether to use
self
or "the thing" at docstrings. This now conflicts with other functions atposets.py
.
comment:3 Changed 5 years ago by
 Commit changed from d40082a97896c42962ef9cb751d38ce0abb4ae28 to da1e421718e66624a3d78a5b9c3681e20f4c8697
Branch pushed to git repo; I updated commit sha1. New commits:
da1e421  trac 21338 more work on posets of intervals

comment:4 Changed 5 years ago by
 Commit changed from da1e421718e66624a3d78a5b9c3681e20f4c8697 to 9edc8601a3f7ea297812be2e575dabe118310d60
Branch pushed to git repo; I updated commit sha1. New commits:
9edc860  trac 21338 more work, not successful

comment:5 Changed 5 years ago by
 Commit changed from 9edc8601a3f7ea297812be2e575dabe118310d60 to 089493916d1b3a518ffb678a5b8197236710f381
Branch pushed to git repo; I updated commit sha1. New commits:
0894939  trac 21338 ready for review

comment:7 Changed 5 years ago by
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 seealsocrosslinks; sorry for not reading this carefully.
comment:8 followup: ↓ 9 Changed 5 years ago by
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 crosslinks ?
comment:9 in reply to: ↑ 8 Changed 5 years ago by
 Reviewers set to Jori Mäntysalo
Replying to chapoton:
Explanation accepted.
Should I remove the crosslinks ?
Yes, I guess so. After that you can click positive_review on behalf of me.
comment:10 Changed 5 years ago by
 Commit changed from 089493916d1b3a518ffb678a5b8197236710f381 to 966bfd4bbf3c7d9e17e29357954e729c18cba7a5
comment:11 Changed 5 years ago by
 Status changed from needs_review to positive_review
done, thanks. Setting to positive
comment:12 Changed 5 years ago by
 Branch changed from u/chapoton/21338 to 966bfd4bbf3c7d9e17e29357954e729c18cba7a5
 Resolution set to fixed
 Status changed from positive_review to closed
New commits:
implement the poset of intervals of a poset