#9972: Add toric lattice morphisms
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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 vbraun):
I agree that the best way is to first convert the input cone to the fan
and then work with that.
But 1) its easy to accidentally omit that step and 2) it is very hard to
detect that you got it wrong. In my book, thats a very dangerous API
design. I don't think a warning in the documentation is sufficient here,
after all, we should have known better yet we fell into that trap with
`ToricDivisor`.
At the very least `ambient_ray_indices()` should spit out a warning if
`self==self.ambient()` [what ARE you trying to do?]. But the best option
seems to me to be the `fan.ray_indices(cone)` method. If you wrote your
code correctly there won't be any slowdown, and if you forgot to convert
the cone to a cone of the fan then you'll still get the right answer.
Ideally we'd then make `ambient_ray_indices` private not use it outside of
`cone.py`/`fan.py` (and fan morphisms).
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9972#comment:26>
Sage <http://www.sagemath.org>
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