External interfaces (was OOC Core Library)

[Mike Griebling <grieblm@trt.allied.com>]

I also would like to define some interfaces to C++ classes.

In particular, it would be nice to be able to call C++ classes with no
overhead very much like a standard Oberon-2 type-bound procedure.  I see
several problems with this:

  1) C++ allows overloaded operators.
  2) C++ allows definition of inline operators (e.g., +, -, etc)
  3) C++ allows structured value returns
  4) Constructors/Destructors may cause some problems

The interface to Oberon-2 would have to redefine overloaded operators
in terms of individual functions with different names.  Inline operators
would be handled as shown below:

     PROCEDURE ["C++", "+"] (VAR c: Complex) Plus (a, b: Complex);

where "+" is an overloaded C++ operator which works with structured complex
values.  Another overloaded function in the same module would be dealt with
as:

     PROCEDURE ["C++", "+"] (VAR c: Complex) PlusReal (a: Complex; b: REAL);

Anyone else have any ideas how to handle this sort of interface?  As well,
does anyone know how C++ deals with class operations and how well they
would map into Oberon-2's type-bound procedures?

In general, our life would be a lot simpler if our compiler supported
structured returns.  We will also have to think about how to deal with
C++ constructors and destructors.  The latter implies that we have some
kind of finalization support.

Michael Griebling