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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Java vs Ada 95 (Was Re: Once again,
 Ada absent from DoD SBIR solicitation)
Date: 1996/11/16
Message-ID: <E0yy3z.1M2@world.std.com>#1/1
X-Deja-AN: 196875317
references: <325BC3B3.41C6@hso.link.com> <1996Nov4.072757.1@eisner>
 <EACHUS.96Nov4182340@spectre.mitre.org> <dewar.848026322@merv>
organization: The World Public Access UNIX, Brookline, MA
newsgroups: comp.lang.ada
Date: 1996-11-16T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <dewar.848026322@merv>, Robert Dewar <dewar@merv.cs.nyu.edu> wrote:
>Suppose we have two variables V1 and V2
>
>We write V1 := V2 (these are unbounded strings by the way)
>
>then we spawn two tasks, T1, T2, then in T1 we assign a completely
>new value to V1 and in T2 we assign a completely new value to V2.
>
>Well this program execution may be erroneous, which is at least to 
>me a bit of a surprise.

I don't see this.  To prove that something is erroneous, you have to
reason from the RM, not from a (possibly incorrect) implementation.  You
can't say, "I choose to implement unbounded strings using erroneous
updates of reference counts (i.e. without locking the counts).
Therefore so-and-so uses of unbounded strings are erroneous."  It seems
to me that the conclusion must be "Therefore this is not a correct
implementation."

- Bob