RE: [boost] SIunits and quantity library concerns

From: Noah Stein (noah_at_[hidden])
Date: 2001-10-04 13:21:07

>(7)  Suppose, instead, these qualifiers function as quantities.  Then
>they represent a measurable attribute and so it would make sense to ask
>in what units they can be measured.  I will therefore ask, "In what
>units can I measure the apple of something?"
>
>(8)  At the moment, I can't satisfactorily answer these questions, and
>hence I tentatively conclude that the concept of qualifiers is
>orthogonal to the concepts of quantities and units.  Can someone argue
>otherwise?

I think you're barking up the right tree on this one.  I think I have an
example that fits your view of the situation: a plane's airspeed vs.
groundspeed.  Both are from the family of quantities Length<>/Time<>.  Both
may be expressed in identical units.  However, the two are semantically
different.

I believe this is analogous to the situation for apples and oranges.  Apples
and oranges, in one scenario, could be considered some sort of
Numeration<>/Price<>, as far as quantity is concerned.  Any of a number of
unit choices could be made.  Both apples and oranges live in the same
quantity/unit space; however, they are semantically different.

My $.02 is that the apples and oranges are a "qualifier" orthogonal to
quantities and units.  If so, the next question is, should support for
qualifiers also be added to a quantity/unit library?  Or is it so orthogonal
that a general-purpose qualifier library should be considered?

-- Noah