From: Jakub Travnik <j.travnik@...>
Date: 2002-04-20T01:49:20+09:00
Subject: Re: Experimental language jtpl

Sean Middleditch wrote:
> On Fri, 2002-04-19 at 08:28, Jakub Travnik wrote:
[snip]
> I might just be an idiot (might? everyone asks), but I don't exactly see
> what the advantage of this is, or even how it's working.  ^,^  How does
> the continuation know about the 
> writenum(10+f()+1000)
> To continue printing the 1110... series?  Also, what is the variable
> passed to cont doing, since I don't see use of an argument or a variable
> anywhere in the above expression or the f() function?

To understand it better look at it in ruby.
This is how ruby can do it too:
-------------------------------
@cont=nil

def f(ret)
   @cont=ret
   return 100
end

counter=0

puts 10+callcc{|r| f(r)}+1000

counter+=1

if counter<4
   @cont.call(counter)
end
-------------------------------

What is advantage of it is more questionable. There is programming
style that uses continuations to make defined order of execution
in pure functional programming languages. Continuations also offers
method to switch between several running procedures explicitly, that is,
cooperative multitasking.

This is of course unrelated to ruby,
but the virtual machine jtpl is running on is related, maybe.


Happy hacking,

Jakub Travnik
jabber://jtra@jabber.com