#9972: Add toric lattice morphisms
-------------------------------------+--------------------------------------
Reporter: novoselt | Owner: mhampton
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-4.6
Component: geometry | Keywords:
Author: Andrey Novoseltsev | Upstream: N/A
Reviewer: Volker Braun | Merged:
Work_issues: switch to FanMorphism |
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Comment(by novoselt):
Oops, sorry - I should have written that it was supposed to be the first.
I unfolded the patches back so that it is clear who is writing/reviewing
what and we don't need to seek the third person for the final review. I
have updated my patch to fix the mistake that you caught. In your part I
have removed `is_equivalent` from `Cone_of_fan` since this optimization is
now performed by general cones. I have also removed extra parenthesis from
`cone = fan().embed(x)`.
I also have one more issue with your patch which got lost above, regarding
new containment check: cones are equal if they have the same rays in the
same order and equivalent if they define the same set of points. If the
same cone happened to sit in different fans (or cones, for that matter)
and so has several different objects representing it, it does not change
anything. We can check if cones belong to the same ambient structure for
code optimization, but the output should be the same. Also, to me it feels
perfectly natural to ask e.g. whether a cone of some fan belongs to a
subdivision of this fan. So I think that `cone in fan` should return
`True` if `cone` is equivalent to any of the cones of `fan`. What is the
ambient structure of `cone` and what is its ray order does not matter. If
you really disagree with this, then I think that `cone in fan` should
return `True` ONLY if `cone.ambient() is fan` is `True`. But I definitely
prefer the first variant. Then one can write
{{{
sage: if cone in fan:
sage: cone = fan.embed(cone)
sage: Do something, say with cone.adjacent()
sage: else:
sage: Deal with it somehow.
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9972#comment:39>
Sage <http://www.sagemath.org>
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