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[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

That should be fairly easy to do, can be handled similarly to Identity.

I = Identity(cell.d)
f = I[i,j] * ...

e = Permutation(cell.d)
f = e[i,j,l] * v[j]*w[i]*v[l]*dx

Other suggestions for naming?

Martin

On 13 April 2011 20:24, Garth N. Wells <gnw20@xxxxxxxxx> wrote:

> The permutation symbol should be added to UFL.
>
> Garth
>
> On 13/04/11 19:20, Martin Sandve Alnæs wrote:
> > Python does not know anything about implicit index summation, so in your
> > code e() is only called once, and reaches the else condition and thus
> > returns 0.0.
> >
> > Similar to as_vector, you can use the as_tensor function, since you need
> > three dimensions.
> >
> > Martin
> >
> > On 13 April 2011 19:04, B. Emek Abali
> > <question152702@xxxxxxxxxxxxxxxxxxxxx
> > <mailto:question152702@xxxxxxxxxxxxxxxxxxxxx>> wrote:
> >
> >     New question #152702 on DOLFIN:
> >     https://answers.launchpad.net/dolfin/+question/152702
> >
> >     May be a non-needed trial for some, but I try to define an
> >     expression (permutation symbol)
> >
> >     def e(i,j,k):
> >            if (i,j,k) == (1.0,2.0,3.0): return 1.0
> >            elif (i,j,k) == (2.0,3.0,1.0): return 1.0
> >            elif (i,j,k) == (3.0,1.0,2.0): return 1.0
> >            elif (i,j,k) == (3.0,2.0,1.0): return -1.0
> >            elif (i,j,k) == (2.0,1.0,3.0): return -1.0
> >            elif (i,j,k) == (1.0,3.0,2.0): return -1.0
> >            else: return 0.0
> >
> >     and use (with summation over indices, it is a curl operator
> >     contracted with w) in the form like
> >
> >     f=v[j]*w[i]*e(i,j,l)*v[l]*dx
> >
> >     which raises:
> >     ufl.log.UFLException: Trying to integrate expression of rank 0 with
> >     free indices
> >
> >     Do I have to use as_vector(...) type definition to sum with indices
> >     or is there a nice possibility to let it sum over the arguments of
> >     e(...) expression?
> >
> >     --
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> >     DOLFIN Team, which is an answer contact for DOLFIN.
> >
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