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From: "Matthew Heaney" <mheaney@on2.com>
Newsgroups: comp.lang.ada
Subject: Re: Re[2]: Limited Type Access - Again
Date: Mon, 29 Oct 2001 18:02:10 -0500
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Date: 2001-10-29T18:02:10-05:00
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<ANH_VO@udlp.com> wrote in message
news:mailman.1004394165.6249.comp.lang.ada@ada.eu.org...
> If equality and assignment are allowed in this case, then it is the back
door
> for comparing and assigning objects of limited type such as task type and
> projected type.

No.  A record type is limited if it has limited components:

task type T;

type RT is
   record
      O : T;
   end record;

O1, O2 : RT;

O1 := O2;  --will NOT compile

if O1 = O2 then --will NOT compile



> I think this door should be locked.

Already done.  This was true already in Ada83.


> In addition, comparing or
> assignment two objects of a task type does not make sense.

It's up to you to decide whether task comparison makes sense.  Note that in
Ada95 you can compare Task_Id's.


>  In fact, the language
> prohibits two objects of a limited type from being compared or assigned.
This is
> the reason why equality and assignment of a limited type are prohibited.

Not quite -- you don't ever have assignment, but you don't have equality *by
default*.  Meaning you can provide your own equality operator for a limited
type:

type RT is
   limited record ... end record;

function "=" (L, R : RT) return Boolean is ...

Or even:

task type TT;

function "=" (L, R: TT) return Boolean is...