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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Interfacing contracts (Was: Eiffel and Java + Ada dispatching)
Date: 1996/11/17
Message-ID: <E11E8r.7LK@world.std.com>#1/1
X-Deja-AN: 197101446
references: <E0KJrC.26o@world.std.com> <E0qKM2.ECw@syd.csa.com.au>
 <6KkYnJwk3RB@herold.franken.de> <56kgrf$61t@fozzie.sun3.iaf.nl>
organization: The World Public Access UNIX, Brookline, MA
newsgroups: comp.lang.eiffel,comp.lang.ada
Date: 1996-11-17T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <56kgrf$61t@fozzie.sun3.iaf.nl>,
Geert Bosch <geert@fozzie.sun3.iaf.nl> wrote:
>Example for interface specification that might be accepted by
>an Ada implementation without violating the Ada-95 standard (yes?):
>
>   --  Integer square root function truncating the exact result
>   function Square_Root (I : Natural) return Natural;
>
>   for Square_Root'Post_Condition use
>      Square_Root (I)  ** 2 <= I and (Square_Root (I) + 1) ** 2 > I;

Well, 13.1(19) says that expression is evaluated at this point, which is
not what you want.

You could use specially-formatted comments, as SPARK does.

By the way, I think invariants (not loop invariants, but per-class
invariants) are the most interesting thing about Eiffel's assertion
facility.

- Bob