[Oberon] How to mimic an associative array

[Duke Normandin]

On Fri, 3 Dec 2010, Douglas G. Danforth wrote:

> On 12/3/2010 9:23 AM, Duke Normandin wrote:
> >   However CGILib would not know in advance
> > what data-type was being passed to it. It has to be able to behave
> > like a dynamically typed language/module. Is that possible in
> > Oberon-2? or with the code that you were so kind to put together?
>
> Duke,
>
> Yes it is possible to define abstract objects whose type at runtime
> can be determined and acted upon accordingly.  Here is an
> example.
>
> TYPE
>      Object = POINTER TO RECORD END;    (* Abstract object *)
>      O1 = POINTER TO RECORD(Object) .... END; (* concrete object *)
>      O2 = POINTER TO RECORD(Object)....END; (* concrete object *)
>      ....
>      On = POINTER TO RECORD(Object)....END; (* concrete object *)
>
>      PROCEDURE Proc (o: Object);
>      BEGIN
>          IF o IS O1 THEN
>              ...
>          ELSIF o IS O2 THEN
>          ....
>          ELSIF o IS On THEN
>              ...
>          ELSE
>              ...
>          END
>
> (PS: you can also use the  operator WITH which casts the object o into
> specific types)

It appears that _all_ the horsepower is available in Oberon-2 for me
to do this project and many others. This CGI module project may be a
bit premature for me. I'll continue on with Nikitin's book, and get
_real_ comfortable doing linked lists and doubles, arrays, records and
pointers using Oberon-2. :) When I can walk the Oberon talk, without
falling on my face, then I'll tackle the CGI thing. I've got one done
in C that I can get ideas from as well. Much obliged!
-- 
Duke