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From: dmitry6243@my-deja.com
Newsgroups: comp.lang.ada
Subject: Re: Parameter Modes, In In Out and Out
Date: Mon, 08 Jan 2001 12:06:48 GMT
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Date: 2001-01-08T12:06:48+00:00
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In article <938p3u$omv$1@nnrp1.deja.com>,
  Robert Dewar <robert_dewar@my-deja.com> wrote:
> In article <3A57CD7F.2228BFD5@brighton.ac.uk>,
>   John English <je@brighton.ac.uk> wrote:
>
> > I prefer to consider parameter passing by copy-and-return
> > rather than by-reference as the norm (even though it applies
> > to fewer situations in practice)
>
> But unfortunately, this model is just wrong for by-reference
> types. Especially in object oriented programming, where all
> tagged types are passed by reference, it is quite wrong to
> regard the input as uninitialized, since this does not
> correspond with the semantics of the language.

OOP does not enforce "tagged types" to be passed by reference. This is
Ada 95 specific. Only class-wide types shall be passed by reference (for
their size is unknown).

Maybe I am wrong, but it seems that RM does not forbid to keep the type
tag separated from the value. Does it?

Anyway the clear distinction of normal types and class-wide types is an
excellent (revolutionaly, IMO) concept. It is pity that Ada 95 didn't
use all advantages of the concept. For instance, to have multiple
dispatch, or even, all types "tagged"!

--
Regards,
Dmitry Kazakov


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