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)?
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.
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
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