I think its fair to call this a bug. I am still shaky on coercions in
Sage so I am hesitant to file a trac report without hearing again from
someone else.
-M. Hampton
On Dec 19, 5:42 am, "David Joyner" <wdjoy...@gmail.com> wrote:
> On Fri, Dec 19, 2008 at 4:57 AM, Jan Groenewald <j...@aims.ac.za> wrote:
>
> ...
>
>
>
>
>
> > sage: A=matrix([[1,2],[2,1]]);A
>
> > [1 2]
> > [2 1]
> > sage: eig=A.eigenvectors_right();eig
>
> > [(3, [
> > (1, 1)
> > ], 1), (-1, [
> > (1, -1)
> > ], 1)]
> > sage: v=eig[0][1][0];v
> > (1, 1)
> > sage: var('t')
> > t
> > sage: type(v)
> > <type 'sage.modules.vector_rational_dense.Vector_rational_dense'>
> > sage: type(v*t)
> > <type 'sage.modules.free_module_element.FreeModuleElement_generic_dense'>
>
> > For instance, I want to subtract v*t from A*v which is not
> > possible in sage.
>
> > I think this would have worked if v*t was of the type
> > sage.modules.vector_rational_dense.Vector_rational_dense
> > just like v. I think it should be that type?
>
> > sage: A*v-v*t
> >
> > ---------------------------------------------------------------------------
> > TypeError Traceback (most recent call
> > last)
>
> ...
>
>
>
> > A workaround we are using in the meantime:
>
> > sage: A*v-v*identity_matrix(2)*t
> > (3 - t, 3 - t)
>
> I'm not sure this is a bug or a missing feature or what but here is
> another workaround:
>
> sage: t^0*A*v-t*v
> (3 - t, 3 - t)
>
> > I still don't get it though, the v*identity_matrix(2)*t has the same type
> > as v*t, why
> > does that even work as a workaround?
>
> > sage: type(v*t)
> > <type 'sage.modules.free_module_element.FreeModuleElement_generic_dense'>
> > sage: type(v*identity_matrix(2)*t)
> > <type 'sage.modules.free_module_element.FreeModuleElement_generic_dense'>
> > sage: type(A*v)
> > <type 'sage.modules.vector_rational_dense.Vector_rational_dense'>
> > sage: type(A*v-v*identity_matrix(2)*t)
> > <type 'sage.modules.free_module_element.FreeModuleElement_generic_dense'>
>
> > I hope that is clearer.
>
> > regards,
> > Jan
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