From: beckwb@ois.com (R. William Beckwith)
Subject: Re: Broadcast facility
Date: Wed, 26 Oct 1994 11:10:52 GMT
Date: 1994-10-26T11:10:52+00:00 [thread overview]
Message-ID: <CyA1q4.6u3@ois.com> (raw)
In-Reply-To: Cy9AJF.Dxy@inmet.camb.inmet.com
In article <1994Oct25.121138.22277@sei.cmu.edu>,
Philip Brashear <brashear@ajpo.sei.cmu.edu> 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
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prev parent reply other threads:[~1994-10-26 11:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
1994-10-25 16:11 Broadcast facility Philip Brashear
1994-10-26 1:04 ` Dale Stanbrough
1994-10-26 1:23 ` Tucker Taft
1994-10-26 11:10 ` R. William Beckwith [this message]
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