A k-tensor (including k-forms) maps k vectors
to a scalar. If k=0, then a 0-tensor maps no vectors
to a scalar, that is, mapping nothing at all to a scalar, or what normal
people would call a plain old scalar. Such forms are created by a
couple of constructions in the package, specifically scalar(),
kform_general(1,0) and contract(). These functions take a
lose argument that behaves much like the drop argument in
base extraction.
Function lose() takes an object of class ktensor or
kform and, if of arity zero, returns the coefficient.
Note that function kform() always returns a kform
object, it never loses attributes.
A 0-form is not the same thing as a zero tensor. A
0-form maps V^0 to the reals; a scalar. A zero tensor
maps V^k to zero.