Re: Typing in Ada

[Wes Groleau <groleau+news@freeshell.org>]

Dennis Lee Bieber wrote:
> On Tue, 01 Jun 2004 02:36:53 GMT, Hyman Rosen <hyrosen@mail.com>

>>limited. In a real program that does something useful, what kinds
>>of things do you want to count up to 100 but not to 101? To 200
> 
> 
> 	[snip good example]

A person's age; you may not know where to put the limit,
but you know you need to do additional checking if you
see 200.

> 	Angular measurements: 0..360 (though likely you'd want some
> floating point type with an upper bound one "step" below 360.0)

If I wanted all responses to be "normalized," I would override
the operators to make it a "modular" float.

But the point of strong typing is that you can't inadvertently
add an Age to the measure of angle AGE.

More important to me than strong typing is abstraction--the
ability to define types whose properties match what they
represent--instead of just being new names for 'int' or 'float'

When these types are numeric in nature, Ada's deriving and subtyping
mechanisms make this simple.  In C/C++/Java you have to do a lot more
work to get the same behavior.  In Java, you CAN'T get the same behavior
with reasonable syntax, since operators are banned from such types.

-- 
Wes Groleau
Alive and Well
http://freepages.religions.rootsweb.com/~wgroleau/