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)
How will vectors be constructed if they can't use this directly? Will you have to create a CoordinateSystem or ReferenceFrame first?

Is there a reason not to let people construct vector directly from the class? It could just default to a default coordinate system if we did. Seem like it would be nice to offer both options. For example, you can create column matrices directly and then do all kinds of operations with them for vector manipulations and not have to think about a coordinate system or reference frame at all.

But I guess, you will never have the scalar variables availble if you construct vectors from the Vector class directly, so maybe that won't work.