From: Ryan Leavengood <leavengood@...>
Date: 2006-05-24T03:06:46+09:00
Subject: Re: How to "go to" in a RUBY script . . .

On 5/23/06, Simen <toalett@gmail.com> wrote:
>
> There's also continuations. They're not only for web frameworks, you
> know. It's fairly easy to write something goto-like with continuations.
> I once did, for fun. You could do stuff like
>
>   label :loop
>     [code]
>   goto :loop
>
> Easy to abuse, fun to write. Still, catch/throw should be sufficient
> most of the time.

This did sound fun, here is my quick and dirty implementation:

$labels = {}

def label(s)
  callcc do |cont|
    $labels[s] = cont
  end
end

def goto(s)
  cont = $labels[s]
  cont.call if cont
end

def method1
  puts "In method1, goto :start"
  goto :start
end

if $0 == __FILE__
  go = true
  label :start
  puts "Starting..."
  if go
    puts "Running loop..."
    i = 0
    label :loop
    puts "i is #{i}"
    i += 1
    goto :loop if i < 5
    go = false
    method1
  else
    puts "Not running loop."
  end
end
__END__

I'm definitely using this in the next obfuscated Ruby contest. In
other words, this should not be used in real code.

Ryan