"Strong typing vs. strong testing"

[Malcolm McLean]

On Sep 27, 9:29 pm, p... at informatimago.com (Pascal J. Bourguignon)
wrote:
>
> On the other hand, with the dynamic typing mindset, you might even wrap
> your values (of whatever numerical type) in a symbolic expression
> mentionning the unit and perhaps other meta data, so that when the other
> module receives it, it may notice (dynamically) that two values are not
> of the same unit, but if compatible, it could (dynamically) convert into
> the expected unit.  Mission saved!
>
I'd like to design a language like this. If you add a quantity in
inches to a quantity in centimetres you get a quantity in (say)
metres. If you multiply them together you get an area, if you divide
them you get a dimeionless scalar. If you divide a quantity in metres
by a quantity in seconds you get a velocity, if you try to subtract
them you get an error.