Re: How come Ada isn't more popular?

[<adaworks@sbcglobal.net>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:1sh134r4r8piq$.wh1w0uitf99t$.dlg@40tude.net...
> On Fri, 09 Feb 2007 07:50:43 -0500, Robert A Duff wrote:
>
>> Maciej Sobczak <no.spam@no.spam.com> writes:
>>
>>
>> Why is that superior to just using functions as constructors?
>> Ada has:
>>
>>     type T(<>) is ...
>>
>> to indicate that clients MUST call some constructor function when
>> creating objects.  And it now allows constructor functions (and
>> aggregates) for limited types.
>
> Because it does not compose upon inheritance and aggregation.
>
> When inherited the constructing function need to be overridden, even if
> null record was the only thing added. Further one can barely publicly
> derive anything from T, which breaks encapsulation.
>
I guess I don't see this as a serious problem.    Perhaps this is because
I frequently take the Modula-2 approach and create opaque types.
These support extensible inheritance, enforce encapsulation, and
separate all the implementation details within the package body.

Granted, the use of opaque types requires the supporting capability
of access types.   But the use of access types in the pursuit of good
programming is no vice.  Rather, it is consistent with the counsel given
us over two score years ago by Maurice Wilkes.

From my perspective, opaque types solve a lot of problems that are
inherent in C++ and Java and support an increased level of separation
of concerns in my application architecture.  That being said, one can,
with a little effort, create C++ opaque types.   I have not thought about
how this would be done in Java. Pehaps through the interface mechanism.

Richard