Re: "Must instantiate controlled types at library level." Why?

[Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>]

On Wed, 19 May 2004 05:20:55 +0400 (MSD), "Alexander E. Kopilovich"
<aek@VB1162.spb.edu> wrote:

>Dmitry A. Kazakov wrote:
>
>> But to have a library you need the language first.
>
>You may be surprised, but I don't think so. More precisely, I don't think 
>that we must have a language in advance or restrict ourselves to a single
>language.

Of course we have to. Things like availability of class-wide
programming, MI, MD, interface inheritance, supertyping etc are
essential for, say, container library. This heavily influences the
whole design. It is C++'s insufficient ADT which led to STL.

>A library is not necessary an extension of a particular language -
>this is just a viewpoint and an approach. Another viewpoint and another
>approach is to build a library as a programming implementation of some
>theory. To have a library with the latter viewpoint/approach we need not
>the language first. We even may postpone decision about the languages that
>we will use (yes, several different languages - why not?) for various parts
>of our library until the design of the library will reach some level of
>refinement. What we need first with this approach is solid theoretical ground
>and clear and consistent requirements for implementation.

In which language those requirements will be written?

>> And as the story of
>> container libraries shows, the languages (both C++ and Ada) seem to be
>> insufficient for this job.
>
>The story of container libraries shows once again already known fact: Ada's
>weakness for *general-purpose* libraries. I think that many Ada.* packages
>suffer one way or another from this weakness.
>
>I guess that from viewpoint of general-purpose libraries, Ada's packages are
>somehow overloaded with various features and restrictions. What is good for
>specific-purpose library may be not so good for general-purpose one.

It is never good.

>I'm not
>calling here for reconsidering of the notion of package (and not because it
>is impossible, but simply because current packages are good enough for
>specific-purpose libraries), but I think that there can be another (i.e.,
>additional) construct, more flexible and less concerned about effectiveness
>(and even about readability

Note that readability is the paramount concern. The whole goal of a
container library to provide a higher level of abstraction. One could
sacrifice efficiency, though I do not see why it is necessary, but not
easiness of use.

> - one may notice that general-purpose libraries
>have much more chances to be supplied with additional materials then most of
>specific-purpose libraries).

The major problem is weakness of Ada's ADT. Unfortunately people keep
on looking in wrong direction. Generics won't help.

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