#11943: The category graph should comply with Python's method resolution order
---------------------------+------------------------------------------------
Reporter: SimonKing | Owner: nthiery
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-4.8
Component: categories | Keywords: category graph, method resolution
order
Work_issues: | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #11900
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Comment(by nthiery):
Replying to [comment:15 SimonKing]:
> I found another detail that may fit here: `Category.is_subcategory`
contains the lines
> {{{
> assert(isinstance(c, Category))
> if isinstance(self, JoinCategory):
> for cat in self._super_categories:
> if cat.is_subcategory(c):
> return True
> return False
> }}}
> First, I don't see why it should be needed to assert that c is a
Category. It seems like a waste of time to me.
As for any reasonable programming language, Python allows to
completely disable assertion tests, to encourage the programmer to put
more safety guards and write programmatically his
preconditions/assertions/..., knowing that in production there won't
be any penalty. Alas, this can't be done on the fly like in MuPAD for
switching between debugging and full speed computation modes inside a
given session (a feature I loved). Still this can be achieved in
principle on a new session by passing -O to the Python
interpreter. Maybe we should add this option to the Sage script
itself.
In that particular case, I guess I once met a bug where something was
passed to is_subcategory which was not a category, so I felt safer
with the assertion test.
> Secondly, the loop does nothing more than to test the cat is in the
> set of super categories of self. So, it can be safely erased. And it
> is a lot faster. ...
> So, my next patch version will remove these lines, provided that doc
tests pass.
I don't remember anymore why I did a special case for join categories,
so +1.
Cheers,
Nicolas
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11943#comment:18>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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