Migrate is_lawrence_polytope and is_pyramid to combinatorial polyhedron

[kliem]

This ticket migrates the methods is_lawrence_polytope and is_pyramid from Polyhedron_base to CombinatorialPolyhedron.

Also, we change the output for the 0-dimensional polyhedron. It is a pyramid over the empty polyhedron, even if it is not constructable in sage.

Along the way we fix a small bug, where the trivial combinatorial polyhedron in dimension 0 was set up without vertices (and facets). The bug fix is tested by CombinatorialPolyhedron(0).is_pyramid(certificate=True).

CC: @jplab @LaisRast

Component: geometry

Keywords: pyramid, lawrence polytope, combinatorial polyhedron

Author: Jonathan Kliem

Branch/Commit: 7e25b29

Reviewer: Laith Rastanawi

Issue created by migration from https://trac.sagemath.org/ticket/29189

[kliem]

New commits:

364a796	migrate is_pyramid to combinatorial polyhedron
3af855d	migrate is_lawrence_polytope to combinatorial polyhedron

[kliem]

Branch: public/29189

[kliem]

Commit: 3af855d

[sagetrac-git]

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

db79f1e

little improvement

[sagetrac-git]

Changed commit from 3af855d to db79f1e

[kliem]

Changed branch from public/29189 to public/29189-reb

[kliem]

Changed commit from db79f1e to c47fc68

[kliem]

New commits:

04cd0cf	migrate is_pyramid to combinatorial polyhedron
7cf6c20	migrate is_lawrence_polytope to combinatorial polyhedron
da9e835	little improvement
c47fc68	applied changes from 28608

[LaisRast]

comment:4

Seems good to me.
Is there a reason why you do not put is_pyramid as a cached method?

[kliem]

Changed commit from c47fc68 to 77433d7

[kliem]

Changed branch from public/29189-reb to public/29189-reb2

[kliem]

comment:5

Well, I never considered caching it, because it is trivial. But I guess it doesn't matter.

---

New commits:

06f9329	migrate is_pyramid to combinatorial polyhedron
ebc9e94	migrate is_lawrence_polytope to combinatorial polyhedron
4f163bf	little improvement
97db2de	applied changes from 28608
77433d7	caching `is_pyramid`

[LaisRast]

Reviewer: Laith Rastanawi

[kliem]

comment:7

Sorry, I forgot the trivial cases.

What is the proper output to polytopes.simplex(0).is_pyramid()?

You cannot construct it as pyramid over one of its faces, because the empty face doesn't have a center.

[kliem]

comment:8

Currently this returns False. Is this reasonable?

[kliem]

comment:9

Then I should add those cases, because currently this just gives a stupid error message.

[LaisRast]

comment:10

Replying to @kliem:

What is the proper output to polytopes.simplex(0).is_pyramid()?

You cannot construct it as pyramid over one of its faces, because the empty face doesn't have a center.

I suggest the output to be True in this case. It does not need to be constructable in sage.

[kliem]

comment:11

I agree. I never liked False either. I'll change it.

[sagetrac-git]

Changed commit from 77433d7 to 7e25b29

[sagetrac-git]

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

7e25b29

fix small dimensional cases

[kliem]

New commits:

7e25b29

fix small dimensional cases

---

New commits:

7e25b29

fix small dimensional cases

[LaisRast]

comment:15

It looks good now.

[vbraun]

Changed branch from public/29189-reb2 to 7e25b29