LatticePoset: add is_join_semidistributive

[jm58660]

This patch will add a function to check if a lattice is join-semidistributive or not.

Backend can also check for meet-semidistributive and give a "certificate", i.e. elements failing the definition of semidistributive. It is not used at this time.

Component: combinatorics

Author: Jori Mäntysalo

Branch/Commit: b4c99b6

Reviewer: Frédéric Chapoton

Issue created by migration from https://trac.sagemath.org/ticket/20714

[jm58660]

Branch: u/jmantysalo/semidistributive

[jm58660]

Commit: 2e264a7

[jm58660]

comment:2

Ready for review, or at least for comments. I don't know about examples, but just now can not invent anything better.

---

New commits:

1e14708	Add is_join_semidistributive().
2e264a7	Removed spaces.

[fchapoton]

comment:3

missing doctest continuation here:

+            sage: H = HasseDiagram({0:[1, 2], 1:[3, 4], 2:[4, 5], 3:[6],
+                                    4:[6], 5:[6]})

[jm58660]

comment:4

And shortcut based on covering relations count is in wrong place.

I don't like this test system that does not detect missing continuation line.

[sagetrac-git]

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

74777e0

Slight modifications.

[sagetrac-git]

Changed commit from 2e264a7 to 74777e0

[jm58660]

comment:6

OK, maybe this works.

It would be a good idea to think about this, not just blindly translate the definition to code. Maybe later.

[fchapoton]

comment:7

typo here:

semidistibutive

[sagetrac-git]

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

9145ac9

Typo correction

[sagetrac-git]

Changed commit from 74777e0 to 9145ac9

[tscrim]

comment:9

You can also use \neq instead of \not=.

[sagetrac-git]

Changed commit from 9145ac9 to 6a3338b

[sagetrac-git]

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

6a3338b

From \not= to \neq.

[fchapoton]

comment:11

another typo

semistributivity

[sagetrac-git]

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

b4c99b6

Another typo.

[sagetrac-git]

Changed commit from 6a3338b to b4c99b6

[fchapoton]

comment:13

looks good to me.

[fchapoton]

Reviewer: Frédéric Chapoton

[vbraun]

Changed branch from u/jmantysalo/semidistributive to b4c99b6