Re: Dimension checking was RE: Why is Ada NOT a good choice for a beginner to programming?

[kcline17@hotmail.com (Kevin Cline)]

"Robert C. Leif" <rleif@rleif.com> wrote in message news:<mailman.1042310041.30777.comp.lang.ada@ada.eu.org>...
> An obvious fix, which was discussed at SIGAda 2002, is to develop a 
> means
> (Pragma?) to tell the compiler to only check the dimensionality at 
> compile
> time. This could be in the form of a compile time assertion.
> Bob Leif

I don't know what the proposal encompassed, but it's hard for me to imagine
an "obvious" fix to this problem.  With physical dimensions we have 
   Qty<L1,M1,T1,...> * Qty<L2,M2,T2,...> => Qty<L1+L2,M1+M2,T1+T2,...>

where L1,M1,T1,L2,M2,T2 are the dimensions of length, mass, time, etc.
However, there are many systems of physical units in use in different
problem domains.  For example, it is often convenient to make length
and time interchangable.

And in matrix algebra we have:
   innerProduct(Matrix<M,N>, Matrix<N,P>) => Matrix<M,P>

Any solution adopted should be able to correctly model 
both of these type systems.