#18529: Topological manifolds: basics
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Reporter: egourgoulhon | Owner: egourgoulhon
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.10
Component: geometry | Resolution:
Keywords: topological | Merged in:
manifolds | Reviewers: Travis Scrimshaw
Authors: Eric Gourgoulhon | Work issues:
Report Upstream: N/A | Commit:
Branch: | 0b08b114e03c063bd2e500ac900fd843fb12673b
public/manifolds/top_manif_basics | Stopgaps:
Dependencies: #18175 |
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Comment (by egourgoulhon):
Replying to [comment:59 tscrim]:
> I've done some small doc/review tweaks,
Thanks for these changes!
> but I was wondering if you were doing any changes to it,
No, not at the moment: I've worked on the subsequent tickets to check if
the introduced changes (in particular the removal of unique
representation) propagate smoothly. So far, so good...
> because I want to do some moderate refactoring to try and simplify the
structure. In particular, you are not really using the subsets as facade
parents as the points know what subset they belong to.
Well, it is true that points have an attribute called `_subset`, but this
is a misnomer: `_creation_subset` would have been better. Indeed, from a
pure mathematical point of view, a point of a manifold has no privileged
subset attached to it. On the contrary, the point belongs to an infinite
number of intersecting subsets. The attribute `_subset`, which is set to
the facade parent at the point creation, is used only for fast check in
the methods `TopologicalManifoldSubset.__contains__` and
`TopologicalManifold.__contains__`. I think it can be suppressed, at the
price of a small decrease in efficiency. Therefore, I still think that the
facade mechanism is appropriate here: the creation subset (i.e. the facade
parent) should not play any role: only the whole manifold matters. This is
particularly true when dealing with tangent planes (ticket #19092): for a
given point p, we do not want to have two tangent spaces, T_p M and T_p U
with U open subset of M, do we?
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Ticket URL: <http://trac.sagemath.org/ticket/18529#comment:61>
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