Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!ut-sally!husc6!rutgers!nysernic!rpicsb8!csv.rpi.edu!hiebeler
From: hiebeler@csv.rpi.edu (David Hiebeler)
Newsgroups: comp.lang.modula2
Subject: Re: Dereferencing of opaquely exported pointers?
Message-ID: <41@rpicsb8>
Date: Tue, 8-Sep-87 13:49:44 EDT
Article-I.D.: rpicsb8.41
Posted: Tue Sep  8 13:49:44 1987
Date-Received: Wed, 9-Sep-87 05:53:36 EDT
References: <14474@topaz.rutgers.edu>
Sender: nobody@rpicsb8
Reply-To: hiebeler@csv.rpi.edu (David Hiebeler)
Organization: RPI CS Dept, Troy, New York
Lines: 15
Keywords: Dereferencing,pointers.

DEC's Modula-2 compiler will not dereference an opaquely declared pointer
from within an external module.  (NEW() gives me a wrong parm type,
^ gives me dereference of a non-pointer).  This seems logical; if the
type is opaquely defined, then one shouldn't be poking around with its
innards from another module.  That's what transparent types are for.
   If you wanted something which was opaque, but still allowed you to
perform those few actions, I suppose you could just export a couple of
procedures from the first module, which were simply calls to the system-
allocations procedures.

                             -D.H.
----
David Hiebeler       hiebeler@csv.rpi.edu
Troy, NY            "Illusions, Richard!  Every
                     bit of it illusions!"