Re: Question about generics.

["Randy Brukardt" <randy@rrsoftware.com>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
news:dv4t30a6porw.1r47tofvyu5ws$.dlg@40tude.net...
...
> Right. But it is the problem of Ada, that "static Positive" cannot be
> expressed as a [formal] type. If that were possible then the generic unit
> could be checked before instantiation. There are also other cases where
> that would be useful. For example, for forcing constant folding at compile
> time (necessary for statically dimensioned values.)

It's not a problem, it's a feature. Repeat after me: a generic is not a
macro. A generic is not a macro. A generic is not a macro. Got it yet?? ;-)

The legality of a generic body never, ever depends on the actual values used
in an instantiation. The legality of a generic spec rarely depends on the
actual values.

In any case, allowing some sort of static generic parameter would completely
prevent any possibility of generic code sharing. It's unlikely that the
language would be changed in such a way.

(If you don't understand why, just consider putting the bit locations for
various types as formal parameters. How would you implement sharing then?)

                           Randy.