🚀 go-pugleaf

Oberon allows procedures to be passed as arguments of other
procedures, and to be stored as components of records: in fact, this
is the basis of Oberon's use in object-oriented programming.  But
there seems to be a language restriction that prohibits the use of
local procedures in this way -- and it seems to me that this resticts
the usefulness of the language in a serious way.

For example, we can define collections that support iterator methods,
but these methods would be more useful if their arguments could be
local procedures.  To give a trivial example:

	PROCEDURE sum(xs: intset);
	  VAR s: integer;

	  PROCEDURE add(x: integer);
	  BEGIN s := s + x END add;

	BEGIN
	  s := 0;
	  xs.do(add);
	  RETURN s
	END sum;

(sorry about the syntax).  This procedure sums a set of integers by
calling the iterator 'do', passing a local procedure that adds each
number to the local variable 's'.  Without local procedures as
parameters, 's' would have to be made a global variable -- Yuk!

Is there any good reason why Oberon doesn't allow this?  I don't seem
to have any serious difficulty in implementing it!

-- Mike Spivey