Re: Constructing an object

[Georg Bauhaus <bauhaus@futureapps.de>]

Randy Brukardt wrote:

> Actually, it wouldn't be that hard to add that to Ada 200Y. We have the
> "overriding" keyword to specify overriding. Additional keywords could
> specify other types of extension -- "extends" perhaps. That would look like:
> 
>     extends
>     procedure Finalize (Obj : in out My_Type);
> 
> or perhaps
> 
>     extends after
>     procedure Finalize (Obj : in out My_Type);
> 
> to specify when the parent routine is called.


AFAICS, the programming language BETA, successor to Simula, has virtual
patterns of the general kind, extending in descendants.
(Everything in BETA is a pattern, "The abstraction mechanisms
include class, procedure, function, coroutine, process, exception and many
more, all unified into the ultimate abstraction mechanism: the pattern.")

Virtual patterns actually use the wording suggested in this thread.

http://www.daimi.au.dk/~beta/Manuals/latest/beta-intro/Introduction.html#H3_1

From
http://www.daimi.au.dk/~beta/Manuals/latest/beta-intro/Virtual.html :

"In fact a virtual pattern in BETA can only be extended and cannot be
completely redefined."

The word "inner" is used to denote a part of a superpattern that is
defined in subpatterns.

From the second URL:

A: (# V:< (# x:  do I1; inner; I2 #) #);
AA: A(# V::< (# y:  do I3; inner; I4#) #)

The pattern A has a virtual procedure attribute V. V has an attribute x
and its do-part contains the execution of I1; inner; I2.
The subpattern AA of A extends the definition of V. The extended
definition of V in AA corresponds to the following object-descriptor
(except for scope rules):

4.3 Combined descriptor

(# x: ; y:  do I1; I3; inner; I4; I2 #)