sympy/sympy — pull request #8423 by smichr (2014-11-11 06:24:27+00:00)
Title: [wip] 8413 and 8373 related changes

See #8413 and #8373

- [ ] check coverage, especially the handling of duplicate args by Xor and Equivalent

(If anybody would like to take this over, that would be fine with me.)