Re: Access keyword

[Adam Beneschan <adam@irvine.com>]

On Apr 30, 12:15 am, Maciej Sobczak <see.my.homep...@gmail.com> wrote:
> On 29 Kwi, 23:32, "Randy Brukardt" <ra...@rrsoftware.com> wrote:
>
> > Anonymous access types (a superset of access parameters) mainly exist in Ada
> > to make it easier for C++ and Java programmers to move their rotten designs
> > to Ada.
>
> Anonymous access types are used by Ada.Containers for iteration (among
> others). "Rationale" by Barnes presents some nice examples with
> downward closures as well.

I suspect that Randy was talking only about anonymous access-to-object
parameters.  Those aren't used by the language's definition of
Ada.Containers, or at least I didn't spot any.

Anonymous access-to-subprogram parameters (which Ada.Containers does
use) are a different animal altogether.  They do serve a legitimate
purpose; downward closures are important but couldn't be done
satisfactorily in Ada 95.  In a way, I think that calling this an
"access" parameter is more of a syntax choice than a real "access"
thingy.  Anonymous access-to-subprogram parameters can't be stored in
variables and thus don't really serve the same purposes as other
access types; for that reason, I think the designers could have done
this without an "access" type, simply by saying they would pass a
procedure or function around, as is done in Algol and Pascal, I
believe.  But doing it as an access type fits in well with the
language rules and syntax that already existed in Ada 95.  Just my
humble opinion here...

[Apologies if this is a duplicate post... Google Groups, which is
apparently written in C++, was not behaving right...]

                                    -- Adam