#10998: Categories for posets
----------------------------------------------------------------------------------+
Reporter: nthiery
| Owner: sage-combinat
Type: enhancement
| Status: needs_work
Priority: major
| Milestone: sage-4.7.1
Component: combinatorics
| Keywords:
Work_issues:
| Upstream: N/A
Reviewer: Franco Saliola, Christian Stump, Nicolas M. Thiéry, Florent
Hivert | Author: Frédéric Chapoton, Christian Stump, Nicolas M. Thiéry
Merged:
| Dependencies:
----------------------------------------------------------------------------------+
Comment(by novoselt):
Replying to [comment:20 nthiery]:
> For the record: finite posets and their elements, now have
UniqueRepresentation. This could have an influence if the same poset is
created several times when constructing several fans.
Yes, this is it. Repeating the failing code twice in the command line
reproduced the error. This raises two questions:
1) Out of curiosity: Why does it show up in doctests? Shouldn't the state
of Sage be clean before running a new test?
2) To the point: How to fix it?
I really don't want to make fans unique at this point as I am planning
some adjustments to them and related objects.
Does uniqueness test rely on `==` test? Is there any way to change it?
Currently `==` for fans checks that fans have the same rays and the same
generating cones in the same order. Things relates to facets require even
stronger `is`-equivalence. On the other hand, Volker votes for `==` being
mathematical equivalence without taking order into account. Such
equivalence definitely would not be acceptable deep inside implementation
which relies on fixed order.
So I guess my preferred solution for now would be to trick posets into
creating different face lattices for fans and cones even if they are `==`.
Can I somehow attach `id(fan)` to the poset without altering its
structure?..
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10998#comment:21>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sage-trac?hl=en.
