🚀 go-pugleaf

Expires:

References:

Sender:

Followup-To:

Distribution:

Keywords:


I have a rather obscure question about SIMULA, and as there doesn't
seem to be a comp.lang.simula, I submit it here for your help.

I am interested in what happens when a prefix A with a virtual
attribute X is accessed from a subclass using `THIS A.X', where
the subclass redefines the virtual.

The intended meaning of THIS A seems to be that the object should be
accessed AS IF IT WHERE AN INSTANCE OF CLASS A, despite the fact that
it might in face be an instance of a subclass.

But I think the way virtuals are implemented will cause THIS A.X to
access the redefined value, not the original one given in A.  Could
someone fix this code and execute it to find out what happens?  Or
send comments on what you think will/should happen.  I will summarize
the results to the net, if there is any interest.

william cook    Brown University     ihnp4!brunix!wrc
-------------------------------------------------------------------
begin
    class A
        virtual : procedure X;
        begin
            procedure X; begin print "ORIGINAL"; end;

            comment execute the procedure;
            THIS A.X();
            inner;
        end

    A class B
        begin
            procedure X; begin print "REDEFINED"; end;

            comment try to run both procedures;
            THIS A.X();
            THIS B.X();
        end;

    comment try them out;
    new A;
    new B;
    comment will probably print ORIGINAL, ORIGINAL, ORIGINAL, REDEFINED;
end