From mboxrd@z Thu Jan  1 00:00:00 1970
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From: dewar@cs.nyu.edu (Robert Dewar)
Subject: Re: What good is halting prob?
Date: 1995/04/20
Message-ID: <dewar.798422571@gnat>#1/1
X-Deja-AN: 101233949
references: <1995Apr19.204744.21914@wdl.loral.com>
 <3n429h$pvu@acmex.gatech.edu> <dewar.798337304@gnat>
 <3n6mru$s87@acmex.gatech.edu>
organization: Courant Institute of Mathematical Sciences
newsgroups: comp.lang.ada,comp.edu
Date: 1995-04-20T00:00:00+00:00
List-Id: <comp.lang.ada>

sorry, no wonder you "don't get it", I messed up the example. here is the
example I meant to give:

   procedure X (a, b : in out string) is
   begin
      a(1) := 'x';
      if b(1) = 'x' then raise program_error; end if;
   end x;

   G : string := "abc";
   X (G, G);

will raise program error if the strings are passed by reference but not
if they are passed by copy. In Ada 83 this program execution is erroneous
and in Ada 95 it is non-deterministic (may or may not raise PE).

Sorry about that!