[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: exporting standard-class

    Date: Fri, 19 Aug 88 14:00:10 EDT
    From: oravax!esrig@cu-arpa.cs.cornell.edu (Bruce Esrig)

    In a previous query, we asked whether there were any problems
    porting pcl to Lucid; we reported that when we make an instance,
    we get a message stating that there is no matching method for
    the generic function initialize-instance.  We now know that
    the cause of the problem was that we had created a class with
    an undefined metaclass.

    The following definition illustrates our problem.
	    (in-package 'my-package :use '(lisp pcl system))
	    (defclass topmost_class (standard-class) ())
	    (make-instance 'topmost_class)

    In this definition, standard-class refers to the internal symbol
    of my-package.  Should the classes standard-class and above be
    exported by the pcl package ?  If they were, this problem would not occur.
    Alternatively, should there be a way to get warning messages when
    forward definitions of class names occur ?

I future versions of PCL, there will be two changes, each of which will
provide you some help with this problem.

1) symbols like standard-class will be exported from the PCL package.

2) attempting to make an instance of a class which has forward
   referenced supers will signal an error.