oliverlee/sympy — pull request #1 by gilbertgede (2013-06-25 00:31:11+00:00)
Title: Consistency w/ 0s in mechanics

Previously, there were inconsistencies in mechanics.essential, with some
methods using S(0) to form empty Vectors and others using an empty Vector
(Vector([])). This has now been corrected to use empty vectors only. The same
is true for the Dyadic class.