[Oberon] Oberon for a C++ user.

[Chris Burrows]

> -----Original Message-----
> From: Oberon [mailto:oberon-bounces at lists.inf.ethz.ch] On Behalf Of
> Stéphane Aulery
> Sent: Friday, 30 September 2016 6:19 AM
> To: ETH Oberon and related systems
> Subject: Re: [Oberon] Oberon for a C++ user.
> 
> >
> > I wonder if there is a way out.  Can this problem be solved within
> the Oberon-1 framework?
> 
> What you say is surprising. There are probably a good reason to
> dismiss this problem. Anybody kwnow why please?
> 

I'd like to see actual example code that illustrates the problem as I am not
convinced it is a problem - at least not with the latest version of Oberon. 
As Srivas pointed out, e.g. in Project Oberon, if you want to assign an
external procedure to a procedure variable, or you want to reference an
external procedure variable you have to import the module that contains that
procedure / procedure variable. If you have imported that module you can't
unload it until the importing module is unloaded first. 

Oberon-2 does have additional object-oriented features. Maybe they cause an
issue when mixed with the use of procedure variables? Procedure Varaiables
might have been left in the language in the transition from original Oberon
to Oberon-2 simply to avoid breaking backward-compatibility. It is likely
there is no *need* to use procedure variables if you have these additional
features. This is supported by the following quote from Hanspeter
Mossenbock's book 'Object-Oriented Programming in Oberon-2':

"Dynamic binding has also been known for a long time in the form of
procedure variables. The activation of a procedure variable causes the
invocation of the procedure contained in it at run time. Working with
procedure variables, however, is troublesome and error-prone, while dynamic
binding in object-oriented languages represents an elegant and reliable
solution."

It is also significant to note that Procedure Variables are documented as
'deprecated' in the .NET version of Component Pascal (the Oberon-2
superset). 

Regards,
Chris

Chris Burrows
CFB Software
http://www.astrobe.com