Right, but ideally A(i, -i, j) and A(j, -i, i) *wouldn't unify. *Actually in this sort of case I suppose that they would because it could be that i == j. Generally speaking though unification variables do need match consistently within a term. (a, a) does not match to (1, 2). Perhaps we could consider all tensor indices on one side to be wild?
On Wed, Apr 2, 2014 at 12:50 PM, F. B. <franz.bona...@gmail.com> wrote: > > > On Wednesday, April 2, 2014 7:35:45 PM UTC+2, Matthew wrote: >> >> Yeah, Wild subclasses from Expr, alas. The logpy solution is to have a >> dispatched isvar function. >> >> It seems to me that the all tensor indices are in some sense wild. >> Shouldn't A[i, -i] unify to A[j, -j] ? >> > > Actually not, that was a particular case because A(i, -i) is A(j, -j), and > this is also equivalent to a scalar (j and -j are summed over). A(i, j) > instead is equivalent to a matrix. If A has associated components data, > A(i, j).data is the N x N ndarray, and A(i, -i) is the trace. > > Consider A(i, -i, j) and A(j, -i, i), these are not equal and should not > unify, not even if both i and j are wild. Of course a tensor constructor > would raise an exception if an index is repeated more than twice. > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > Visit this group at http://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/d7b6882e-d224-48b9-8261-bd5ff81cb84c%40googlegroups.com<https://groups.google.com/d/msgid/sympy/d7b6882e-d224-48b9-8261-bd5ff81cb84c%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAJ8oX-HT3JZoytpCALYsB9p91FdjwYfzQ5HF8seM2KgY%3D2Pf-Q%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
