Re: Types with physical dimension

[dewar@cs.nyu.edu (Robert Dewar)]

"Of course it would be nice to have more direct support for units"

In the "of course" here likes a rather fundamental assumption which I
question, namely that it is always desirable to have features at hand
that do exactly what you want in the most convenient way. While that
may seem locally optimal, I am afraid that following this inclination
repeatedly leads to too much complexity in language design. Remember
that a reader must be able to read the code, that means that a reader
has to be able to pretty much understand the whole language since there
is no restriction on what the writer can write. A big language is not
so bad from the writer's point of view, since you only learn what you
need, but from the reader's point of view, the complexity is much
harder to handle.

To me, the units case crosses the line. I think you can build this well enough
in Ada, esp in Ada 9X with the abstract feature, and I think that (even
given infinite resources :-) it would be a mistake to add an additional
(inevitably somewhat complex) feature that would handle this more
directly.