#13814: LazyFamily.__eq__ gives false positives.
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Reporter: cnassau | Owner: sage-combinat
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.6
Component: combinatorics | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Christian Nassau | Merged in:
Dependencies: | Stopgaps:
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Comment (by cnassau):
Replying to [comment:6 nthiery]:
> Replying to [comment:2 cnassau]:
> > The TestSuite failures would probably be fixed if `_test_pickling`
would check for
> > {{{
> > not (f != loads(dumps(f)))
> > }}}
> > rather than
> > {{{
> > f == loads(dumps(f))
> > }}}
> > I'll suggest this in a different ticket.
>
> ``__eq__`` and ``__ne__`` are supposed to be implemented consistently;
so
> _test_pickling is allowed to rely on this assumption. If the
> assumption fails, that's an equality bug which should be fixed in
> ``__eq__/__ne__`` and be tested in ``_test_equal`` (whenever possible).
Well, I think it __is__ consistent to have
{{{
sage: LazyFamily(Integers(),lambda i:i) ==
LazyFamily(Integers(),lambda i:1*i)
False
sage: LazyFamily(Integers(),lambda i:i) !=
LazyFamily(Integers(),lambda i:1*i)
False
}}}
In my reading this conforms to the standard python requirements:
hashing only requires `__hash__` and `__eq__` in
`http://docs.python.org/2/reference/datamodel.html#object.__hash__`
The document also says
There are no implied relationships among the comparison operators. The
truth of x==y does not imply that x!=y is false.
Cheers,
Christian
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13814#comment:8>
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