Hi, On 25 April 2012 01:36, Tom Bachmann <[email protected]> wrote:
> On 25.04.2012 00:20, Aaron Meurer wrote: > >> On Tue, Apr 24, 2012 at 5:16 PM, Tom Bachmann<[email protected]> wrote: >> >>> I agree. Can you open an issue for this in our issue tracker >>>> (http://code.google.com/p/**sympy/issues/list<http://code.google.com/p/sympy/issues/list> >>>> )? >>>> >>>> We can do hypergeometric series, which is why the summation() function >>>> is so powerful in the git master, but I think it's not recognizing >>>> this one as such because it's a finite sum (Tom, please correct me if >>>> I'm wrong). If you use the fact that binomial(n, k) == 0 for k> n, >>>> and replace n with oo in the summation limits, you get: >>>> >>>> >>> I was about to say precisely that. >>> >> >> So any thoughts on how to fix it. I guess we should try to recognize >> if the summand is zero for all but finitely many values. And then do >> some manipulation on the indices. >> >> > Hm. I'm not really sure. I think that this example work by evaluating an > infinite sum is a bit of a curiosity. I think for finite sums, in general, > a different algorithm is needed (we have gosper_sum, but that apparently > does not apply here). I'm afraid I'm not very knowledgeable on this subject. Gosper's algorithm doesn't work when upper limit is involved in summation term. You need Zeilberger's algorithm for this (at least for hypergeometric terms). > > > By the way, I just noticed: >> >> In [156]: summation( binomial(n,k), (k,n - 1, oo)) >> Out[156]: >> ⅈ⋅π >> n - ℯ >> >> That exp_polar() should probably be evaluated in the result. >> >> > Yeah I'll submit a pull request for that tomorrow. > > > Aaron Meurer >> >> > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to sympy+unsubscribe@** > googlegroups.com <sympy%[email protected]>. > For more options, visit this group at http://groups.google.com/** > group/sympy?hl=en <http://groups.google.com/group/sympy?hl=en>. > > Mateusz -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
