sympy/sympy — pull request #1697 by jrioux (2012-12-19 15:06:15+00:00)
Title: KroneckerDelta in discrete summations and products

This is a little bit like deltaintegrate is to DiracDelta. Fixes the following issues:

Handle KroneckerDelta in Sum
http://code.google.com/p/sympy/issues/detail?id=3481

Handle KroneckerDelta in Product
http://code.google.com/p/sympy/issues/detail?id=3482