[Oberon] Clarifying type compatibility in Oberon-07

[Jörg]

August

>>> * Under "Assignment compatible" you don't mention assignment of open arrays.
>> 
>> open arrays only exist as formal parameter of a procedure not as a variable. Assignment rules are for variables. In my point of view open arrays are covered in Array rule 2.
    
> I'm talking about paragraph 4 in section 9.1 of the Oberon-7 language 
>    	a: ARRAY 10 OF INTEGER;
>    	b: ARRAY 10 OF INTEGER;
>	a := b;

9.1.1 is covered by Assignment rule 5
9.1.2 is covered by Assignment rule 6
9.1.3 is covered by Assignment rule 3
9.1.4 is indeed an interesting one

Here an example to demonstrate what 9.1.4 says:

VAR global: ARRAY 20 OF INTEGER;

PROCEDURE A (open: ARRAY OF INTEGER)
  VAR local: ARRAY 10 OF INTEGER
  BEGIN
    local := open (* this is mentioned in 9.1.4 *)
  END A;

BEGIN
  A(global)   (* this is covered by Array rule 2 *)
END.

Two remarks:
Indeed 9.1.4 is not covered by any of the existing rules of Appendix A.
On the other hand, I can’t find where your example of a := b is mentioned in the Oberon-07 report (independent of the fact that the compiler allows it..)

br
Jörg