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Newsgroups: comp.lang.ada
Date: Wed, 6 Sep 2017 18:29:06 -0700 (PDT)
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Subject: Re: Why does Ada.Iterator_Interfaces specify Next as a function
 rather than a procedure?
From: Stephen Leake <stephen_leake@stephe-leake.org>
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Xref: news.eternal-september.org comp.lang.ada:47961
Date: 2017-09-06T18:29:06-07:00
List-Id: <comp.lang.ada>

On Wednesday, September 6, 2017 at 8:04:15 PM UTC-5, Stephen Leake wrote:
> >      type State is record
> >           -- The components of the state.
> >      end record;
> > 
> >      type My_Iterator is new Ada.Finalization.Controlled and 
> > Reversible_Iterator with record
> >            My_State : access State; -- Writable state.
> >            The_State : aliased State;
> >      end record;

I don't see how to do this; 'Reversible_Iterator' is defined in an instantiation of Ada.Iterator_Interfaces, which takes the type My_Iterator as a generic parameter.

Just leaving that off still fails, if I try to make the contents of the cursor private while exposing the Iterate function.

Are you relying on some new Ada 202x syntax here?
> > 
> >      procedure Initialize (Obj : in out My_Iterator) is
> >      begin
> >           Obj.My_State := The_State'Access; -- (*)
> >      end Initialize;
> 
> > This is a legitimate technique -- it is NOT erroneous in Ada 
> > 2012 -- so if your compiler has problems with it, file a bug report and if 
> > they don't believe that, send me a proposed ACATS test!
> 
> You are implying that my worry about the compiler assuming the input and output of Next must point to different items is not valid.
> 
> I'll give it a try.
> 
> -- Stephe