LatticePoset: Add meet_irreducibles, faster is_distributive

[jm58660]

Finite lattice posets now has join_irreducibles() and join_irreducibles_poset(). Add meet_irreducibles() and meet_irreducibles_poset().

is_distributive() is now based on formal definition. It can just check that lattice is graded and that number of both meet- and join-irreducibles equals to rank (=height-1) of the lattice.

CC: @nathanncohen

Component: combinatorics

Author: Jori Mäntysalo

Branch/Commit: 8b68cdb

Reviewer: Nathann Cohen

Issue created by migration from https://trac.sagemath.org/ticket/17121

[jm58660]

Branch: u/jmantysalo/latticeposet__add_meet_irreducibles__faster_is_distributive

[jm58660]

New commits:

0ee134c

Much better is_distributive(). Added two little functions.

[jm58660]

Commit: 0ee134c

[jm58660]

Author: Jori Mäntysalo

[nathanncohen]

Reviewer: Nathann Cohen

[nathanncohen]

comment:3

Hello !

1. meet_irreducibles: you write len(self.upper_covers()) which calls upper_covers_iterator which iterates over all out-neighbors of a vertex of the HasseDiagram before relabelling them as !Poset elements. Why ? All you want to do is check that the outdegree of those points if 1. You could work on the diagram directly.

2. Please add the new functions to the index.

3. You cannot use $ for latex code there. Use ` instead. In order to check that the doc compiles correctly run sage -b && sage -docbuild reference/combinat html and look at the html files produced.

4. Use () instead of \ to wrap code on multiple lines.

Nathann

[jm58660]

comment:4

1: But posets.py says "This internal data structure is subject to change at any point. Do not break encapsulation!" But I can do that of course; then I'll also change join_irreducibles.

2: Uh, of course.

3: OK. But then http://www.sagemath.org/doc/developer/coding_basics.html#latex-typesetting needs correcting.

4: OK.

[sagetrac-git]

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

b3e1bca

Minor corrections.

[sagetrac-git]

Changed commit from 0ee134c to b3e1bca

[jm58660]

comment:6

3: It seems that $ works in me. Could you check it? 2: There is no index where to add... So, more work to poset documentation project.

As of 1, I did not do that for now; this is direct copy from join_-counterparts. Point 4 is done, but long line of == is still quite hard to read.

Also this same time I removed totally unused argument from cover_relations. Is this OK to do in ticket title saying nothing about it?

[nathanncohen]

comment:7

Yo !

1: But posets.py says "This internal data structure is subject to change at any point. Do not break encapsulation!" But I can do that of course; then I'll also change join_irreducibles.

Lost computations for political reasons. This code never ceases to amaze me :-P

3: OK. But then http://www.sagemath.org/doc/developer/coding_basics.html#latex-typesetting needs correcting.

Oh. If it is written in the developper's manual then the nazis can do nothing against you. Good ! :-D

Nathann

[nathanncohen]

comment:8

2: There is no index where to add... So, more work to poset documentation project.

Oh, no index for lattices. Right, sorry for my remark !

As of 1, I did not do that for now; this is direct copy from join_-counterparts. Point 4 is done, but long line of == is still quite hard to read.

As you wish. Remember that there is some time there to save if you have time problems later on.

Also this same time I removed totally unused argument from cover_relations. Is this OK to do in ticket title saying nothing about it?

I don't mind. It will depend on the reviewers, though.

I will run all tests on a machine to check that removing this keyword does not break anything somewhere.

Nathann

[tscrim]

comment:9

The dollar-sign $ does work, but it is (strongly?) recommended that you use the backticks ` instead. I think there are still issues with the notebook's documentation when using dollar-signs.

[sagetrac-git]

Changed commit from b3e1bca to 8b68cdb

[sagetrac-git]

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

8b68cdb

Changed "$" to "`" as LaTeX marker on documentation.

[nathanncohen]

comment:11

All tests passed !

Thanks,

Nathann

[vbraun]

Changed branch from u/jmantysalo/latticeposet__add_meet_irreducibles__faster_is_distributive to 8b68cdb