T o d d P a t t i s t wrote:

the span into that function and evaluate it. It's never a
vector.

Two ways to describe the same thing. (Reminds me on Newton and
Bernoulli... shall we start? :-) But I agree that the function picture
is more natural.

As a side note, this is getting kind of tangential to
aviation.

Not too surprizing in this group.

Stefan