#19555: Implement a containment for cartesian_product
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Reporter: tscrim | Owner: sage-combinat
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.10
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: Travis Scrimshaw | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
public/sets/contains_cartesian_product-19555|
fb14675d6a264ca2405cebbcdb62a3eddfadd1f4
Dependencies: | Stopgaps:
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Comment (by vdelecroix):
Replying to [comment:2 ncohen]:
> I admittedly do not know much about such matters, but isn't the problemm
here that the object is not a 'facade' object, while you expect it to be
in your bug report?
More or less. The current generic code (from `sage.structure.parent`)
tries to compare the tuple with the corresponding object of the cartesian
product. And they of course compare as different:
{{{
sage: C = cartesian_product([srange(5), srange(5)])
sage: c = C((1,1))
sage: c
(1, 1)
sage: c == (1,1)
False
sage: (1,1) == c
False
}}}
Warning: your example is completely broken
{{{
sage: C = cartesian_product([range(5), range(5)])
sage: C((1r,1r))
(1, 1)
sage: C((1,1))
Traceback (most recent call last):
...
TypeError: Cannot convert int to sage.structure.element.Element
}}}
Warning++: you can not use `range` and `srange` in the same Sage session
since `FiniteEnumeratedSet` uses `UniqueRepresentation`... I guess a safer
way to implement this unique representation, would be to force a common
universe for the elements... (see #19562)
--
Ticket URL: <http://trac.sagemath.org/ticket/19555#comment:4>
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