Updates:
Summary: What should summation() do with non-integer limits?
Status: Accepted
Cc: [email protected]
Labels: Concrete
Comment #1 on issue 2723 by asmeurer: What should summation() do with
non-integer limits?
http://code.google.com/p/sympy/issues/detail?id=2723
You're doing a summation with non-integer limits. I'm not sure if this
even should be allowed, and if so, if it should be defined as you want it
to be. The expression you get comes from plugging -0.5 and 0.5 into the
general forumla:
In [11]: print summation(f, (x, n, m))
(exp(a*n) - exp(a*m + a))/(-exp(a) + 1)
To get what you want, I would recommend restructuring your summation to use
integer limits. For example:
In [8]: print summation(exp((a - 0.5)*x), (a, 0, 1))
exp(0.5*x) + exp(-0.5*x)
Mateusz, you've studied this more than I have. Are summations with
non-integer limits well-defined, and if so, do you think we should allow
them?
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