Make ppl mutable

[kliem]

We allow for ppl polyhedra to be mutable.

This is a preparation for allowing interactive modification. At the moment not much can be done, but to delay the calculation of Vrepresentation and Hrepresentation.

The goal is that normaliz and polymake use Polyhedron_interactive as well and allow adding generators/inequalities.

Depends on #32157

CC: @jplab @mkoeppe @yuan-zhou

Component: geometry

Keywords: ppl, lazy double description

Author: Jonathan Kliem

Branch/Commit: fce9f98

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/32158

[mkoeppe]

comment:2

How about "mutable" instead of "interactive"

[mkoeppe]

comment:3

And surely by default, polyhedra should remain immutable, right?

[mkoeppe]

comment:4

IMO, the constructor Polyhedron should get an additional keyword argument immutable=True (unfortunately there's a bit of inconsistency - in the Sage library one finds all three of immutable=, is_mutable=, is_immutable=).
When False, it should select a suitable backend

[mkoeppe]

comment:5

See also #29101 for my proposed "Refined protocol for _element_constructor_ in element classes with mutability"

[kliem]

comment:6

Thanks for the comments. Yes, using immutable is much better. I would prefer to not have another backend though. It's the same with vectors and matrices. One can just make them immutable, if one likes to, but not the other way around.

[mkoeppe]

comment:7

Replying to @kliem:

I would prefer to not have another backend though.

I'm just saying that Polyhedron, if no backend is given and is_mutable=True is passed, should select one of the backends that support mutation. As of this or a follow-up ticket, I guess that's only ppl.

[sagetrac-git]

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

8dceb88	Polyhedron_interactive -> Polyhedron_mutable
5124844	add _element_constructore_polyhedron for ppl over ZZ
c82c144	remove copy paste typo
2cfd7a5	Merge branch 'u/gh-kliem/small_improvements_ppl' of git://trac.sagemath.org/sage into u/gh-kliem/lazy_ppl
d4f6fb7	remove redundant lines in test

[sagetrac-git]

Changed commit from 86be3ed to d4f6fb7