Re: anonymous access type

[Adam Beneschan <adam@irvine.com>]

On Mar 5, 9:50 am, Hibou57 (Yannick Duchêne)
<yannick_duch...@yahoo.fr> wrote:
> On 5 mar, 16:05, Robert A Duff <bobd...@shell01.TheWorld.com> wrote:
>
> > Do you find it strange that we don't have:
>
> >     X : constant Integer := 123;
> >     Y : variable Integer := 456; -- Not Ada!
>
> > ?
> > - Bob
>
> Well done, you've got a clever point indeed.
>
> Perhaps the reason why I did not miss is beceause it does not belong
> to the same side. When I see in/out on parameters, I see it from the
> external user point of view (e.g. I'm looking at it as a user who
> would like make a reference to it), while when I see your exemple, I
> see it from the inner point of view (e.g. I'm inside a procedure/
> function).
>
> You know what ? I oftenly miss something else : beside of the
> formal_parameter_selector_name [ARM2005 6.4/5], I would enjoy in/out
> hints at the call statement, just to make invokation instances more
> clear when a procedure can modifiy its parameters. It it not always
> easy to state it in the procedure's name or in the parameter's name.
>
> But perhaps I'm a bit mad (may be the "explicit" concept is becoming a
> kind of hard drug)

I think Ada 79 or some earlier proposal had that.  For named parameter
associations, instead of the => syntax we've gotten used to:

   Proc (Param => Expression);

the syntax was

   Proc (Param := Expression);

for IN parameters;

   Proc (Param =: Variable);

for OUT parameters, and

   Proc (Param :=: Variable);

for IN OUT parameters.  At least that's what I recall from way back
when.  I suppose the language could still allow

   Proc (Param <=> Variable)

for IN OUT, but of course <= has another use now so we couldn't use
that...

And I think that in Ada 79, this was only possible for named
associations, not positional ones.

I don't think your idea is a bad one, though, to allow (but not
require) IN|OUT|IN OUT keywords in front of actual parameters (named
or positional).  The implementation effort for compiler maintainers
would be small, I believe.

                              -- Adam