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From: steve.folly@rdel.co.uk (Steve Folly)
Subject: generic formal object parameters of mode 'in out'
Date: 2000/11/06
Message-ID: <3a06dc1c.259466533@news.rrds.co.uk>#1/1
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X-Trace: rdel.co.uk 973528953 12265 172.21.185.71 (6 Nov 2000 16:42:33 GMT)
Organization: RDEL
NNTP-Posting-Date: 6 Nov 2000 16:42:33 GMT
Newsgroups: comp.lang.ada
Date: 2000-11-06T16:42:33+00:00
List-Id: <comp.lang.ada>

Hi,

While reading the ARM today I noticed it's possible to specify generic
formal objects of mode 'in out'.

I was just wondering what use this could have?

Para 12.4 [1b] does state that it's like a renaming declaration of the
explicit actual parameter.

In my program I have the following generic package...

subtype Template_String is string(1..4);

generic
   type T is private;
   Default : T;
   Template : Template_String;
package P
   The_Template : constant String := Template;
   .
   .
end P;


We have had to declare The_Template because we've found that the
parameters are not visible from an instantiation, ie.

declare
  package X is new P ( T => Integer, Default => 0, Template => "NNNN"
);
begin
   Ada.Text_Io.Put_Line("The template is " & X.Template ); -- uh oh!
   Ada.Text_Io.Put_Line("The template is " & X.The_Template ); -- OK
end;

Am I right in thinking that by making Template an 'in out', I don't
need The_Template.

And, if it is now an 'in out', can I change Template at any time
outside of the instantiation (or inside it) ?

Just my disjointed ramblings at the end of long day...

Cheers,
Steve Folly.