Re: Ada exception block does NOT work?

[Martin Krischik <krischik@users.sourceforge.net>]

Maciej Sobczak wrote:

> Note that those other languages can throw regular objects as exceptions,
> thus enabling polymorphism when they are handled.

It is interesting to note that Java and C# has reversed from C++ not
allowing any object to be thrown - but only object which are "Throwable".

Besides: can you throw C++/Java/C# exception across Threads, Processes or
Distributed (from on computer to the next over a network). You can with
Ada.

> One could say that 
> this is the point of good integration and that Ada's exceptions are a
> conceptual patch that did not integrate with the rest of the object
> model, leading to two separate spaces of language entities instead of
> only one.

Well Ada 83 had exceptions but not objects with dispatching so exceptions
could not be objects.

In fact this is one point you should remember: Ada 83 hat exceptions,
generics, well defined type system with type extension for primitive (int,
emum, etc. pp) types and a concept for "private".

The only thing which was missing and was added with Ada 95 where objects as
a C++ would see then.

C++ programmers often see Ada object as something bolted on - and I too had
some problems - but once you understand how it works you will see that it
is far better integrated into the language then in C++.

Surprised? Well Ada 95 had a concept of "RTTI" right from the beginning - in
C++ RTTI was bolted on later. And because Ada had "RTTI" right from the
beginning Ada does not need those "clone ()" functions often suggested in
C++ and Java tutorials. In Ada can clone any object without the aid of
clone () or Clonable.

How it works? Read:

http://en.wikibooks.org/wiki/Ada_Programming/Subtypes#Indefinite_subtype
http://en.wikibooks.org/wiki/Ada_Programming/Object_Orientation#The_class-wide_type

Martin
-- 
mailto://krischik@users.sourceforge.net
Ada programming at: http://ada.krischik.com