Basic vector code, without a coordinate system class

All calculations essentially occur in the same frame.
i, j, k and x, y, z are imported as base vectors and base scalars by default on importing sympy.vector.
delop is a Del operator instance.

Example:

>>> v = 3*i - j
>>> delop ^ v
0

(delop ^ v represents curl of v)
This would work as well, but turns out to be computationally more expensive than the method I have used. It leads to almost twice the number of Vector initializations, as compared to the method involving generation of the components first, and then passing all of them to <code>VectorAdd.\_\_new\_\_</code>