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From: Robert A Duff <bobduff@world.std.com>
Subject: Re: Pb with use of redefined "=" operator
Date: 1998/11/10
Message-ID: <wccvhkn89ud.fsf@world.std.com>#1/1
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Sender: bobduff@world.std.com (Robert A Duff)
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Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada
Date: 1998-11-10T00:00:00+00:00
List-Id: <comp.lang.ada>

Brian Rogoff <bpr@shell5.ba.best.com> writes:

> I agree that certain "small" data types are best not tagged, but I would
> think that a collection in general is not such a type.  ...

I'm not so sure.  Suppose you give me a package that implements a
reusable "list of things" type.  And suppose I'm writing a compiler, and
I want to use that type to represent the parameter lists of function
calls in the parse tree.  Well, I need to be able to deal with fairly
long lists, and write all my algorithms to deal with any length, but I
suspect the *average* list length in this case would be about 1.2 items
(just my guess!).  So adding an extra word of storage for a bogus tag
field is a lot, if I don't need it.  So in that case, I don't want to
use the "reusable" code.

> Unfortunately, it has many, many flaws.

Indeed.  They all do.  But this field is still pretty young.

>... The real pity is that I don't
> think that there are really any better languages out there in the same
> language design space. Maybe one day someone will design a successor to 
> Ada unencumbered by backwards compatibility (*).  

Backwards compatibility was indeed the most difficult design constraint
on Ada 9X.  I've heard similar comments from Stroustrup about C and C++.

But backwards compatibility is what everybody wants.  Even Java has a
form of backwards compatibility -- it sort of looks like C, on the
surface.

> (*) No, Eiffel isn't even close, IMO.

But it has some good ideas in it, too.

- Bob
-- 
Change robert to bob to get my real email address.  Sorry.