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Newsgroups: comp.lang.ada
Subject: Re: Constant record components
From: Georg Bauhaus <bauhaus@futureapps.de>
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Date: Sat, 01 Jul 2006 20:33:08 +0200
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Date: 2006-07-01T20:32:53+02:00
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On Sat, 2006-07-01 at 10:37 -0700, ME wrote:

> What I meant was components that can not be changed after the record 
> components are initialized.
> I can not use Record discriminanats because I have a two dimensional 
> unconstrained array of these records.

You could use "component notation" with a suitable function in Ada 2005,


package rec is

   type R is tagged private;

   function make(m: INTEGER) return R;
      -- `m` is the initial value for the immutable component

   function immutable(thing: R) return INTEGER;

private

   type R is tagged record
      mutable: INTEGER;
      data: INTEGER;
   end record;

   pragma inline(immutable);
end rec;


   x: rec.R;
   n: INTEGER;
begin
   n := x.immutable;  -- Ada 2005
   x.immutable := n;  -- illegal to assign to function result