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From: Ted Dennison <dennison@telepath.com>
Subject: Re: OO puzzle
Date: 1999/12/23
Message-ID: <83tb9t$g8e$1@nnrp1.deja.com>#1/1
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In article <83sqht$5oi$1@nnrp1.deja.com>,
  Ehud Lamm <mslamm@mscc.huji.ac.il> wrote:
> In article <83qtap$pri$1@nnrp1.deja.com>,
>   Ted Dennison <dennison@telepath.com> wrote:
> > if d not in truck_driver'class then
> >    raise Constraint_Error;
> > end if;
> >
>
> Right. But than we are dealing with a runtime check. See the
> discussion per Tucker's post.

Well...yes. But even if the language directly supported MI, this would
have to be a runtime check in many situations. Situations where it
doesn't dynamicly dispatch might be determinable at compile time, but in
those situations you don't need straight inheritance either.

The real drawback in my mind is that the type constraint isn't visible
in the procedure's spec. You'd have to copiously comment it, but
comments aren't checked by the compiler.

--
T.E.D.


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