From: Mikael Brockman <mikael@...>
Date: 2004-08-21T07:55:56+09:00
Subject: Re: ruby, actors, continuations, Kernel#callcc

zuzu <sean.zuzu@gmail.com> writes:

> reading carl hewitt's seminal paper on the actor model:
> http://www.lcs.mit.edu/publications/specpub.php?id=762
> my current impression is that actors are basically pure-OO objects
> using continuations (coroutines?) instead of stack-frame
> methods/subroutines.  this way objects only require "promises" (in the
> form of the passing of context) rather than the final value (as with
> method stack-frames).  (i think this important towards breaking free
> from von neumann architecture, ala bachus:
> http://delivery.acm.org/10.1145/360000/359579/p613-backus.pdf?key1=359579&key2=7975779801&coll=portal&dl=ACM&CFID=11111111&CFTOKEN=2222222
> 
> but i still can't quite seem to grok continuations, at least in terms
> of interpreting it for ruby, w/r/t closures and Kernel#callcc.  this
> after reading dan "parrot" sugalski's weblog
> [http://www.sidhe.org/~dan/blog/], jim weirich's email
> [http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/78288
> ], and rubygarden/c2.com/wikipedia articles on the subject:
> http://www.rubygarden.org/ruby?action=history&id=Continuations
> http://rubygarden.org/ruby?ContinuationExplanation
> http://www.ruby-doc.org/docs/ProgrammingRuby/html/ref_c_continuation.html
> http://c2.com/cgi/wiki?ContinuationExplanation
> http://en.wikipedia.org/wiki/Subroutine
> http://en.wikipedia.org/wiki/Coroutine
> 
> 
> any futher help is much appreciated.

For me, there wasn't really an a-ha moment, at which point I immediately
grasped the implications of CALL/CC.  Rather, I kept playing around with
it, and after I while I just found myself understanding.

Nevertheless, if you want more stuff to read, you can try
http://mikael.phubuh.org/Media/Writing/Continuations/.  I'm not much of
an educator, but at least it uses Ruby.

  mikael