ma., 14.03.2011 kl. 11.00 -0700, skrev Ondrej Certik:
> On Mon, Mar 14, 2011 at 3:11 AM, Øyvind Jensen <jensen.oyv...@gmail.com>
> wrote:
> > Alexander, All,
> >
> > How is it going with your tensor implementation? I put together some
> > code to implement variance of tensors and uploaded it to github in my
> > tensor_contractions branch [0]. If you would like to build on that,
> > feel free to do so. If you have already made your own implementation,
> > please just choose whatever works best for your framework.
> >
> > Here is how it works in the advertised branch:
> >
> > >>> A = IndexedBase('A')
> > >>> i = VarIdx('i')
> > >>> A[i.up, i.down]
> > A[^i, _i]
> > >>> get_indices(A[i.up, i.down])
> > (set(), {})
> > >>> get_indices(A[i.up, j.down]*x[j.up])
> > (set([^i]), {})
>
> This is great! Once either of these implementations is in sympy, I'll
> update the relativity example to use it.
That would be very cool! What would be a good way to connect the
abstract tensor objects to its concrete representations? Perhaps
something like sympy.utilities.implemented_function could work?
Øyvind
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