Re: Ada Components (was Java Portability)

[Brian Rogoff <bpr@shell5.ba.best.com>]

On Tue, 7 Aug 2001, Lao Xiao Hai wrote:
> When Ivan Stepanov decided to build the STL, 

You've already been corrected on the name, it is Alexander. 

> he began with Ada 83 but
> found the template model (generics) inadequate, and the inability to do
> extensible inheritance to be a liability.

Actually, he and David Musser started with Scheme. They later produced the 
Ada version. I don't believe inheritance was an issue; if anything
Stepanov believes that OO is OOverhyped. 

> He switched to C++ and that is now where the STL has its most mature
> representation. 

While he was at ATT with Stroustrup is when templates were being designed. 
Many of his library desires fed right in to the C++ template design. 

> Stepanov has
> been variously supported financially by AT&T, HP and Silicon Graphics,
> and perhaps by others.    No one is supporting anyone, at present, to build
> an equivalent set of libraries for Ada, even though the 1995 Ada standard
> addressed and surpassed the concerns originally raised by Stepanov.

That's both true and false. Ada 95 is great in some ways, lousy in others, 
from the standpoint of building C++s STL. C++ has a crude form of
parametric polymorphism, and Ada generics, which must be explicitly
instantiated and named, are just *not* the same thing as parametric
polymorphism. Given the differences, I think copying the STL too closely
will just make Ada look bad. 

Ada does have a half decent approach to signatures now (which looks 
really primitive and clunky to any ML user) which is nice when building an
STL because you get compile time checking. 

There's some work on "generic programing" in the FP community, which has a
more mathematical flavor, and has some of the same goals as the C++ work, 
but is almost entirely different, and is, like most work from the FP 
community (and unlike C++ :), beautiful. 
 
As far as the rest goes: why do you think anyone working on an Ada project
would pay for an Ada STL? They'd either use free Ada libraries or switch
to C++ and not pay for the C++ STL. 

-- Brian