LatticePoset: join and meet of several elements

[jm58660]

Enhance join() and meet() to accept a list as an argument. If empty list is allowed, return the top/bottom element.

CC: @nathanncohen

Component: combinatorics

Author: Jori Mäntysalo

Branch/Commit: 51aa0ae

Reviewer: Nathann Cohen

Issue created by migration from https://trac.sagemath.org/ticket/17231

[jm58660]

Branch: u/jmantysalo/latticeposet__join_and_meet_of_several_elements

[sagetrac-git]

Commit: 8095cf3

[sagetrac-git]

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

8095cf3

Enhanced meet() and join() to accept a list of elements as argument.

[jm58660]

Author: Jori Mäntysalo

[jm58660]

comment:3

I also removed old example from three years old bug.

[nathanncohen]

comment:4

Hello !

I do not understand why you do

i, j = map(self._element_to_vertex, (x,y))
return self._vertex_to_element(self._hasse_diagram._meet[i,j])

and not only

x=(x,y)

Short of that, you updated the docstring of "join" but did not do the same for "meet".

AAAannd I think that it is all :-)

Nathann

[jm58660]

comment:5

Replying to @nathanncohen:

I do not understand why you do

i, j = map(self._element_to_vertex, (x,y))
return self._vertex_to_element(self._hasse_diagram._meet[i,j])

and not only

x=(x,y)

I do not understand what you don't understand. :=)

I the function get an element of the lattice as an argument, say 'a', it must convert it to "element" of the Hasse diagram, get meet and convert back. Maybe instead of map it would be better to have just

i = self._element_to_vertex(x)
j = self._element_to_vertex(y)

Or do you mean to remove part I marked as "Handle basic case fast" to comments?

Short of that, you updated the docstring of "join" but did not do the same for "meet".

True. Must correct this.

[sagetrac-git]

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

51aa0ae

Docstring of meet() corrected.

[sagetrac-git]

Changed commit from 8095cf3 to 51aa0ae

[nathanncohen]

Reviewer: Nathann Cohen

[nathanncohen]

comment:8

Hello !

Well, I thought that you could save some time but now I do not see it anymore O_o

It feels a bit weird to compute the top element, and compute its meet with something else given that you already know the result but well, it does not matter much I guess.

Good to go !

Nathann

[vbraun]

Changed branch from u/jmantysalo/latticeposet__join_and_meet_of_several_elements to 51aa0ae