sympy/sympy — pull request #1269 by gilbertgede (2012-04-29 20:58:04+00:00)
Title: Better checks for Vectors, Dyadics in mechanics

The code for checking if an input was a vector or dyadic needed to be improved,
as 0's were "slipping by" sometimes (a 0 integer). Also, consistently returns 0-vectors
rather than 0-integers from operations (same for dyadics).