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From: "Dmitry A. Kazakov" <dmitry@gandalf.atm.fh-luebeck.de>
Subject: Re: Subverting 'Access for Sub-programs
Date: 1999/08/11
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NNTP-Posting-Date: 11 Aug 1999 14:42:51 GMT
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Date: 1999-08-11T14:42:51+00:00
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Robert Dewar wrote:

> The discussion we were having is what should be done to the
> language design if you abandon this annoying non-technical
> consideration.
>
> It is in that context that I suggest that Unchecked_Access
> would be appropriately allowed for subprograms with the
> obvious semantics (if you absolutely *must* think in
> implementation terms, the static link semantics that you
> mention above :-)

I believe that the actual problem is in using pointers. In 90%, I would
say, there is
no need to pass a subroutine by pointer. It should be passed by
reference: What we
need is something like (syntax is imaginary):

    type function ARealFunction (X : float) return float;

    function Integral (F : ARealFunction; From : float; To : float)
return float is
    begin
       ...
    end;

The key difference is that the function object must exist only at the
call point which is
clear from argument profile. The callee is unable to get its address and
store it.

In remaining 10% the restrictions on 'Access are meaningful and require
no back doors.

Regards,
Dmitry