#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:
Authors: Eric Gourgoulhon | Work issues:
Report Upstream: N/A | Commit:
Branch: | 6dec6d592a09e56921b9a761827309dd31ae2533
public/manifolds/top_manif_basics | Stopgaps:
Dependencies: #18175 |
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Comment (by tscrim):
Some things from looking over the current structure:
- I would separate out parts of the subset class that applies to
`Top(ological)Manifold` and `TopManifoldSubset` into an ABC (abstract base
class) so you don't have to do things like `self is manifold`.
- Maybe put the subsets into the `Subobjects` class and maybe consider not
making it a facade?
- Should manifolds and their subsets be `UniqueRepresentation`? I
understand that the name as the only input means they are essentially
treated as variables, but it means you have to do things like
`TopManifold._clear_cache_()` (which may be needed not just necessarily in
doctests if one does this before the gc comes around).
- Related to the above, we want parents to be hashable and have a good
equality. I know that by making it a `UniqueRepresentation`, many of these
issues are solved. However the manifolds are essentially mutable, but by
doing a `__hash__` which only depends upon the name(s) and dimension means
this is okay (`__eq__` defaults to check by `is`). This would alleviate
the need for `UniqueRepresentation`.
- In the tests for `_element_constructor_`, you shouldn't call it
explicitly but via `X(...)`, which also checks that it is working
correctly with the coercion framework.
- I don't quite agree with checking `self._field == RR` for real charts as
the precision should not matter. I would check `isinstance(self._field,
RealField)` instead. Granted, we probably should have a function that
checks against all known real field implementations...
- In a similar vein, I don't like the input of `'real'` to `RR` (and
`'complex'` to `CC`). I would make the user be explicit about what they
want unless you are doing to do some special handling to make this pass
special arguments to an underlying `SR` implementation.
--
Ticket URL: <http://trac.sagemath.org/ticket/18529#comment:27>
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