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From: Adam Beneschan <adam@irvine.com>
Newsgroups: comp.lang.ada
Subject: Re: Unconstrained Arrays
Date: Wed, 25 Mar 2009 15:03:36 -0700 (PDT)
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Date: 2009-03-25T15:03:36-07:00
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On Mar 25, 2:21 pm, sjw <simon.j.wri...@mac.com> wrote:
> On Mar 20, 3:45 pm, Adam Beneschan <a...@irvine.com> wrote:
>
> > On Mar 19, 11:45 pm, sjw <simon.j.wri...@mac.com> wrote:
> > Hope this helps explain things.  In any case, I strongly agree with
> > everyone else that using pointers in the OP's particular situation is
> > the wrong approach, and there shouldn't be any reason for it except
> > perhaps to work around a poor compiler implementation.
>
> Thanks for the explanation.
>
> My current problem is with this ..
>
>    type Stream_Type
>      (Buffer : access Ada.Streams.Stream_Element_Array)
>    is new Ada.Streams.Root_Stream_Type with private;
>    --  Provides an in-memory Stream over the elements of Buffer.
>    --
>    --  When one of these Stream_Types is created, it is notionally
>    --  empty. If Buffer is not in fact empty (perhaps it has been read
>    --  from a datagram socket), use Set_Last to indicate the index of
>    --  the last valid element.
>
> where having to initialize a buffer of size 2048 (say) with useless
> data and then overwrite it by reading from a socket goes against the
> grain. Perhaps I'll be able to find the Ada way of doing it and it
> will be suitably elegant.

Well, you can initialize it with garbage data instead of useless data:

   Buffer : aliased Ada.Streams.Stream_Element_Array := (1 .. 2048 =>
<>);

A minor improvement, maybe.  I do think this is clunky, though, but I
don't know what the answer is.  A worse problem is that there are
contexts where this workaround is disallowed.

                                 -- Adam