From: Robert Dober <robert.dober@...>
Date: 2007-06-07T06:03:07+09:00
Subject: Re: code problems

On 6/6/07, Rick DeNatale <rick.denatale@gmail.com> wrote:
<snip>
> Robert, you are right, it loops in ruby, but not in irb.
>
> I was trying to cook up a simple example and got hoist by irb's petard.
>
> What happens in ruby is that calling the continuation goes back to the
> method, which returns to the point before the cont.call and away we go
> again.
That confirms my limited understanding of it :)
>
> Continuations normally aren't reused in the way I did in the example.
> I'm actually not sure why it works the way it does in irb.
Hmm maybe I can give some hint in my zenwalk ruby 1.8.6 irb it loops
as well as in my Windows (one click installer) irb, do you use a
special irb setup?
>
> Here's a simpler example which shows the flow of control concept.
>
> rick@frodo:/public/rubyscripts$ cat testcontin.rb
> def continuation
>   puts "Before callcc"
>   callcc {|cc| puts "In callcc";return cc}
>   puts "After callcc"
> end
>
> puts "Begin"
> cont = continuation
> puts "Got cont #{cont.inspect}"
> if cont
>   cont.call
>   puts "After call"
> end
> puts "All done"
> rick@frodo:/public/rubyscripts$ ruby testcontin.rb
> Begin
> Before callcc
> In callcc
> Got cont #<Continuation:0xb7de3840>
> After callcc
> Got cont nil
> All done

That is a good example I really like to build on it.
Thanks.

Maybe I might add one thing which took me some minutes to work out ;)
the nil value for the cont variable comes from :   puts "After call".

Cheers
Robert
-- 
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw