The biological cell (was: Erlang)
ducasse
ducasse at iam.unibe.ch
Sun Nov 16 08:41:45 UTC 2003
Hi alan
did you read our last OOPSLA paper on APL and Smalltalk?
Philippe Mougin and Stéphane Ducasse, OOPAL: Integrating Array
Programming in Object-Oriented Programming , In Proceedings OOPSLA 2003
(International Conference on Object-Oriented Programming Systems,
Languages and Applications), October, pp. 65--77, 2003, PDF
http://www.iam.unibe.ch/~scg/Archive/Papers/Moug03aOOPALOOPSLA.pd
Philippe did a really good job at integrating APL power with message
passage. I hope to find a good student to see how we could deeply
integrate that in Squeak. Philippe is also interested and ready to help
in the port by giving the Objective-C code.
Stef
> Hi Rob --
>
> At 6:19 PM -0800 11/14/03, Rob Withers wrote:
>> Alan, these posts are always so stimulating. Could
>> you tell me a little about abstact algebras and how
>> you relate them to computers sending messages to other
>> computers? Is it related to defining languages, in
>> some way?
>
> Originally, algebra was a symbolic form of arithmetic. In the 19th
> century, mathematicians realized that there were lots of other systems
> that had some of the properties of numbers, and they gave such systems
> with various overlaps to numbers, names such as groups, fields, rings,
> etc., and algebras. This then became a useful metaphor and goal: to
> try to find common properties of systems and abstract them into the
> simplest schemes that covered all of them. So, e.g, a number of the
> object-like systems I saw in the 60s, such as Sketchpad, used a
> particular offset in the layout to find the pointer to (say) the
> display subroutine for that kind of object. Today we call that
> polymorphism, but this term is borrowed from theory of functions and
> is not quite right. In any case, once you have an inside and an
> outside, and try to do everything through embedded procedures of some
> kind, you have set up the possibility for an "algebra" of meaning that
> could extend over all objects. Clearly, a good job of this cuts down
> the size and nomenclature of the concept space. This thinking was
> before APL, but not before Iverson's book that defined a more
> comprehensive version of APL, and it occured to me that you could go
> much further than Iverson did with what I called "generic procedures".
>
>>
>> you also wrote:
>>
>>> An interesting consequence of this structure was
>>> that protection was
>>> complete in ST-72, and all messages could be
>>> serialized if the object
>>> wanted (we did not bother with this because we were
>>> working on
>>> different kinds of problems -- but Hewitt thought
>>> about it a lot).
>>
>> Could you say a little more about why protection was
>> ensured?
>
> In the very same way that a computer on the Internet is quite
> intrinsically safe -- no outside entity can force anything because the
> computer has to run some of its own code before anything can be
> admitted and acted upon. To hurt a computer it has to have stupid and
> foolable SW. The ST-72 objects were only given a pointer to the
> message and the knowledge that a message was trying to be sent. They
> had to do the rest of the work to receive the message, and they had
> full power to act or not.
>
>> Also, I like the implications of serializing
>> all msgs. How did this work in these systems?
>
> As I said, we didn't do very much about this, but part of the style
> that the first Simula used, and the later Hewitt Actors inspired by
> ST-72 were very much concerned about serializing. Again, thinking of
> an object as a computer, it was quite possible to make objects that
> would implement ques, etc., that would handle or reject messages in
> serial order. This is part of Dave Reed's scheme in his '78 MIT thesis
> and in his part of Croquet.
>
> Cheers,
>
> Alan
>
>>
>> thanks!
>> journeyman rob
>
>
> --
>
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