Hi. This sounds like a good suggestion. Based on the name, _remove_repeated, does remove duplicates, but this can done without removing the ordering.
Aaron Meurer On Mon, Jun 4, 2018 at 4:20 AM, Andrew D. Hanlon <ddhan...@gmail.com> wrote: > Hello Everyone, > > I've been using sympy in my research for several months now, and it has been > really great! I have a suggestion for a possible improvement. I have been > making extensive use of the tensor modules, and I deal with indices quite > frequently. > > My issue lies in the function 'get_indices' defined in the > tensor.index_methods module. This function returns all of the free indices > (i.e. non-repeated indices in an expression). But, every time this function > gets called, the order in which the indices are returned is random. I would > find it quite useful if the indices were returned in the same order that > they appear in the expression passed to 'get_indices', or at the very least > in a determined order. > > The random order can be traced to the function '_remove_repeated' (also > defined in the tensor.index_methods module). In the line right before the > return of that function, the list 'inds' contains all the free indices in > the same order that they appeared in the expression passed to 'get_indices'. > Then, when the function returns it creates a set from this list which > destroys the ordering. I would suggest that the '_remove_repeated' function > does not convert 'inds' to a set. > > My guess for why this was converted to a set in the first place was to > ensure the uniqueness of the elements in 'inds'. However, it seems that the > elements in 'inds' are already unique. But, even if they were not, there are > probably some other ways to ensure this that don't spoil the ordering. > > What do others think of my suggestion? > > Thank you, > --Andrew Hanlon > > -- > 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 https://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/CACO9nak03Qo%2BVTXV2x%3D%3DbcJHtPe_hwz2NtvWDYknZO4d7uAr8Q%40mail.gmail.com. > 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 https://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6KWr5%2BBOkho6nenTZAusi8jCxnqJV%2Bm_ukZxRRLSAR_1g%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
