Re: Another Idea for Ada 20XX

["chris.danx" <chris.danx@ntlworld.com>]

"Mark Lundquist" <mlundquist2@attbi.com> wrote in message
news:KoMO7.2339$Px.45566@rwcrnsc54...
>
> Yes.  Units do need to be primitive.
>
> I've been thinking about this for a while too, but haven't had the chance
to
> write it up.  The idea frankly never occurred to me until Ehud suggested
it
> in a post a few months back.  At first I thought "that's nuts".  But it
> isn't :-)...
>
> We now have type-safe programming in Ada.  But there are two things
wanting:
> (1) unit-safe programming, and (2) automatic unit conversion.  These
cannot
> be provided without augmenting the language.  (Note: "automatic" does not
> mean "implicit", it means the compiler does the work for you).
>
> This would really complete Ada's support for scalar abstraction.
>
> "James Rogers" <jimmaureenrogers@worldnet.att.net> wrote in message
> news:3C0A5054.E74A82E7@worldnet.att.net...
> >
> [snip...]
> >
> > Possible declarative syntax might be:
> >
> > type Meters is unit range (0.0..1.0E380);
> > type Hours is unit range (0.0..9.99E30);
>
> Something like that.  I don't think this is going to cut it, but you're on
> the right track....  Unit declarations need to be independent of types.



> Then a dimensioned type would be created by combining a unit with a
> representation later on, in the type definition.  You need to defer the
> "binding" of a type to a unit in order to achieve the right level of
> abstraction.

> > type Speed is unit(Meters / Hours);
>
> I think the correct approach would involve declaring a unit (but not a
type)
> in terms of Meters and Hours (in your example).  The programmer would want
> to call this unit "Meters_Per_Hour", not "Speed".