sympy/sympy — pull request #2198 by zanzibar7 (2013-06-20 18:49:32+00:00)
Title: factor, expand, subs improvements to Sum

- introduce _eval_factor for recursive-calling
- added _eval_expand and _eval_factor features for Sum
- new implementation of Sum._eval_subs
- use C.Add and C.Mul instead of Add and Mul
- additions to test_sums_products.py