Re: Parameter Modes, In In Out and Out

[dmitry6243@my-deja.com]

In article <93e4e6$ucg$1@nnrp1.deja.com>,
  Robert Dewar <robert_dewar@my-deja.com> wrote:
> In article <93cagm$c1j$1@nnrp1.deja.com>,
>   dmitry6243@my-deja.com wrote:
> > 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"!
>
> It is NOT "using all advantages of [a] concept" to insist that
> it be used absolutely everywhere. On the contrary, that kind of
> approach leads to a much more restrictive and less useful
> expressive power.

If you meant under the concept "to be used everywhere" the type based
distinction between things that dispatch and things that do not",
then I do insist (:-). Do you disagree?

If the concept is an ability to derive from a type, then please note
that already in Ada 83, one had an ability to derive from any type:

type XX is new X;

How could this be "restrictive"?

> As for multiple dispatch -- people can disagree -- but I think
> the designers of Ada 95 were pretty much unanimous in rejecting
> consideration of MD -- it's far too much complexity for far too
> little gain. (please note, MD /= Multiple Inheritance -- the
> two concepts are unrelated).

Yes "people" disagree (:-). IMO both MD and MI are a rigid must,
just because they are closures of the concepts of having a dispatching
parameter and of having a base type.

Single dispatch is like to have overloading involving exactly one
dedicated parameter. I am well aware of artefacts of MD. Nobody says
that MD is simple. But single dispatch is simply wrong for binary
operations. (Nice that Ada at least enforces same tag for all
dispatching parameters. In C++ the situaltion is catastrophic). It
is better not to use a thing at all than to use it incorrectly.

--
Regards,
Dmitry Kazakov


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