From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,8e64f4db20d57eb5
X-Google-Attributes: gid103376,public
From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Call by reference vs. call by value
Date: 1996/07/23
Message-ID: <DuztI8.7EL@world.std.com>#1/1
X-Deja-AN: 169640586
references: <31F10E50.726@egr.uri.edu> <dewar.837995690@schonberg>
 <Duy5ur.4Dt@world.std.com>
 <Pine.SUN.3.91.960723082703.22250A-100000@erlang.praxis.co.uk>
organization: The World Public Access UNIX, Brookline, MA
newsgroups: comp.lang.ada
Date: 1996-07-23T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <Pine.SUN.3.91.960723082703.22250A-100000@erlang.praxis.co.uk>,
Peter Amey  <pna@erlang.praxis.co.uk> wrote:
>This is another Ada feature well covered by the SPARK subset.  The rules 
>of SPARK (which are checked by the SPARK Examiner) prohibit all cases 
>of aliasing where program meaning might be affected by the parameter 
>passing mechanism used. A SPARK program has copy-in, copy-out semantics 
>regardless of the compiler used to compile it.

Right, but you could equally well say that a SPARK program has by-ref
semantics.  SPARK ensures that the two are equivalent by avoiding
aliasing, as you said, and also by avoiding exception handlers.

- Bob