Re: Ada 200X

["Robert I. Eachus" <rieachus@attbi.com>]

Larry Kilgallen wrote:

> Presuming your survey is accurate, what basis is there to think this
> would persist if Ada were widely used in a greater variety of domains ?

It is not a matter of the nature of domains, but of the nature of Ada. 
Try it and see.  A great test is a library of container classes.  At 
first you thing that you are going to have a four or five deep 
hierarchy.  After working on it a bit you conclude that there are two 
(or three depending on who is doing it)* top level classes, and all the 
other classes are children of those.  Why is this so different from 
other OO languages?  Me I 'blame' it on information hiding and the Ada 
culture. If you create a complex structure of derived in Ada, that 
reveals some implementation details to the user, or prevents the 
implementor from choosing the best way to implement a feature. Two sides 
of the same coin.

*Hey wait a mimute you say, remembering the original Booch components, 
you need tasking and non-tasking versions, and this and that, and... 
Right, but at the base you have various forms of structures with 
sequential access, and those with keyed/random access.  (The potential 
third category above is bags and other structures without unique keys.) 
  But a tasking safe singly linked list, a non-tasking safe doubly 
linked list, and a stack are all different implementations of a single 
interface abstraction.

Whether we get interface as a keyword in Ada 0Y or not, the parent is an 
abstract limited private type, and all the children are slightly 
different implementations.  If you want you can actually have some 
non-abstract subprograms in the parent, but in practice the ones you can 
inherit are one liners anyway.