#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):
Aha, now I see! I really don't like the idea of forced arguments to
`ambiet_ray_indices` and `get_cone` seems to be a confusing name. How
about this:
1. Implement `get_cone` functionality using `__call__` for fans and
cones, i.e. you will have to write `fan(c).ambient_ray_indices()` to make
sure that indices are correct. The same goes for other relative things
like face walking methonds - in all cases it is assumed that your cone
knows where does it sit. This goes very well with the concept of fans
being collections of cones - you "convert" a certain cone to an element of
this collection. For cones it is not as transparent but still makes
perfect sense, IMHO.
2. In principle, I don't terribly mind adding *optional* argument so that
one can write `c.ambient_ray_indices(fan)` and internally it will be
translated to `fan(self).ambient_ray_indices()`. However, I then want to
have it for all functions where it does make sense, it will add the same
piece of code and documentation to all of them, and in the user code it
does not lead to any significant clarification or space saving. So I'd
rather not add such functionality and you don't usually like having two
different ways to do the same thing ;-)
3. Leave equivalence and containment checks mathematical, i.e. it is
possible to get `True` for a check that a cone of one fan is "in" another
fan. Those who want to check if it is an actual element of the collection
should use `cone.ambient() is fan`.
If you agree with these proposals, then I can start implementing them and
uniqueness of cones (and then fans too for uniformity, I guess) working on
top of your patch.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9972#comment:21>
Sage <http://www.sagemath.org>
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