Re: MCL and communications...

[reti@cambridge.apple.com (Kalman Reti)]

At  2:30 PM 12/9/93 +0000, John R. Gersh wrote:
>In article <9312091035.AA22471@laforia.ibp.fr> Eric JACOPIN writes:
>>What would be the simplest way to make MCL programs (each running on a separate
>>mac connected with appletalk) communicate LISP structures ?
>
>Use appleevents. Look at the appleevent-toolkit.lisp and
>eval-server.lisp files in the examples folder of the MCL distribution.
>There's a bit of learning (and Inside Mac reading) involved if you haven't used appleevents before, but once that hurdle is passed setting up the
>communication is relatively simple.
>
>
>---------------------------------------------------------------------
>John Gersh                              John_Gersh@aplmail.jhuapl.edu
>The Johns Hopkins University Applied Physics Laboratory
>Johns Hopkins Rd., Laurel, MD 20723                    (301) 953-5503

John Gersh's answer is just what I would have said.  However, there are some issues
in the attempt to "communicate LISP structures" which bear addressing.  If these
structures are all able to be printed readably, then you can merely do a print on one
end and a read on the other.  If they aren't, then you have to invent special code which
puts the lisp structure into a form that can be shipped over to the other machine and
reconstructed.  In the most general case, you might even have to worry about structure
sharing and circularity of references among objects, so this part could actually be
non-trivial.

There is also another orthogonal set of issues w.r.t. error recovery and restarting in case
the receiver and/or the sender have either resource problems which cause appleevents to
be lost or complete crashes.  Of course, without knowing your application's requirements,
I have no idea if you need to go into that.