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From: "Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org>
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Subject: Re: Constant record components
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Date: Sat, 01 Jul 2006 21:44:09 GMT
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Date: 2006-07-01T21:44:09+00:00
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Georg Bauhaus wrote:
> 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.
> 
> 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
...
> end rec;

    A : Rec.R := Rec.Make (1);
    Y : Integer;

    X : constant Integer := Rec.Immutable (A);
begin
    A := Rec.Make (2);
    Y := Rec.Immutable (A);

    if X = Y then
       Ada.Text_IO.Put_Line ("Component is constant");
    else
       Ada.Text_IO.Put_Line ("Component is not constant");
    end if;

You get 3 guesses which string is output, and the 1st 2 don't count. 
Clearly, this does not meet the OP's interest in components that cannot 
be changed after initialization.

-- 
Jeff Carter
"When danger reared its ugly head, he bravely
turned his tail and fled."
Monty Python and the Holy Grail
60