On Tue, Jul 26, 2011 at 11:55 AM, Rob Beezer wrote:
> I've built a class for vector space morphisms, aka linear
> transformations. Mostly this just extends free module morphisms,
> while making a few distinctions between behavior for vector spaces
> versus modules over rings. Everything seems to be working fine, but I
> cannot get equality testing to work.
>
> Equality testing of free module morphisms ends up in a __cmp__()
> method for "matrix morphisms." My vector space morphisms extend free
> module morphisms, which in turn extend matrix morphisms. If f and
> g are two free module morphisms, then
>
> f == g, f.__eq__(g), f.__cmp__(g)
>
> all employ the matrix morphism method __cmp__() and do the right
> thing. However, if f and g are two of my vector spaces morphisms,
> then f.__cmp__(g) does the right thing, but f == g and
> f.__eq__(g) give the wrong answer (False for equal morphisms) and
> never "reach down" to employ the __cmp__ method in the base matrix
> morphism class.
>
> Any hints, or places to look for guidance? No amount of searching the
> developers guide, reference manual, or forums has landed me in the
> right place. A 95%-complete patch is up at
> http://trac.sagemath.org/sage_trac/ticket/11556
> which has all the details, but there is little point in wading through
> all that, unless you were interested in reviewing it once
> complete. ;-)
>
Did you overload *both* __cmp__ *and* __hash__?
William
>
> Thanks,
> Rob
>
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--
William Stein
Professor of Mathematics
University of Washington
http://wstein.org
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