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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