From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=BAYES_00,INVALID_DATE autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,1087b2696d1f5370 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 1994-10-26 07:49:36 PST Newsgroups: comp.lang.ada Path: nntp.gmd.de!xlink.net!howland.reston.ans.net!EU.net!uunet!ois!beckwb From: beckwb@ois.com (R. William Beckwith) Subject: Re: Broadcast facility Message-ID: Organization: Objective Interface Systems, Inc. X-Newsreader: TIN version 1.2 PL2 References: <1994Oct25.121138.22277@sei.cmu.edu> Date: Wed, 26 Oct 1994 11:10:52 GMT Date: 1994-10-26T11:10:52+00:00 List-Id: In article <1994Oct25.121138.22277@sei.cmu.edu>, Philip Brashear wrote: >-------- --- ------ ----- --- -- -------- - --------- ------- -- --- >Question: Has anyone shown how to simulate a broadcast command in Ada? >-------- --- ------ ----- --- -- -------- - --------- ------- -- --- If you asking about broadcast in the Smalltalk sense, it is easy in Ada 9X. i.e. each object has a list of dependents. If the state of an object is changed it sends its list of dependents an update message. In Smalltalk this capability is inherited from the root Object class. It is interesting to note that this mechanism wreaks havoc on garbage collectors and reference counting schemes. If Object D is a dependant of Object P, then you don't want Object P's reference to Object D to cause Object D to continue to exist. ParcPlace's product has `weak' reference which is ignored by the garbage collector for just this purpose. We have had to create a similiar weak reference to support Fresco's broadcast mechanism in a reference counting environment. ... Bill -- e-mail: Bill.Beckwith@ois.com | Team Ada Objective Interface Systems, Inc. | dist, full O-O 1895 Preston White Drive, Suite 250 | multithreading Reston, VA 22091-5448 U.S.A. | built in