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From: Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Anybody in US using ADA ? One silly idea..
Date: Fri, 31 Jan 2003 09:38:51 +0100
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Date: 2003-01-31T09:38:51+01:00
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On Thu, 30 Jan 2003 13:01:17 -0500, Hyman Rosen <hyrosen@mail.com>
wrote:

>Dmitry A. Kazakov wrote:
>> But you don't. It is already here.
>
>But someone does.
>
>> You just reuse it, because int is to some extent a subtype of double.
>
>No, because int is convertible to double.
>
>Besides you, I haven't heard anyone else
>who would consider that to be subtyping.
>Indeed, any time I encounter such type
>lattices they always seem enshrouded in
>confusion.

There is no agreement on definition of subtyping. Most widely used is
LSP-subtyping defined in terms of substitutability. In the spirit of
this definition int is an in-subtype of double, because int is
substitutable for double in in-mode [as my example with fabs shows].
Further, the compiler makes this substitution automatically (no matter
how), so one can say that int inherits, imports [whatsoever] fabs from
double.

---
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de