From: Kirk Haines <khaines@...>
Date: 2006-05-23T10:19:48+09:00
Subject: Re: How to "go to" in a RUBY script . . .

On Monday 22 May 2006 6:04 pm, Louis J Scoras wrote:

> Precisely what I was thinking.  The spaghetti code problem is largely
> attributed to non-local use of flow control.  I do miss being able to
> easily jump out of a nested loop, and with the labeling construct Phil
> refers to I think it's pretty readable.

The Ruby way involes a little more typing than the Perl way, but it seems 
pretty easy to me:

-----
tc = 0

catch(:bailout) do
  while true
    tc += 1
    throw :bailout if rand(50000) == 1
  end
end

puts "Bailed out after #{count} iterations."
-----

I like this.  It's very flexible.  It lets me pass data out of the dark inner 
place that the execution path is escaping from, and it will let me nest 
catch() statements if I want.

Another silly, slightly more complex example:

-----
def do_iterations
  iterations = Hash.new {|h,k| h[k] = 0}
  tc = 0
  while true
    tc += 1
    iterations[0] += 1
    while tc % 100 != 0
      tc += 1
      iterations[1] += 1
      while tc % 10 != 0
        iterations[2] += 1
        tc += 1
        throw(:bailout,[tc,iterations]) if rand(50000) == 1
      end
    end
  end
end

count,iterations = catch(:bailout) {do_iterations}
puts "Bailed out after #{count} iterations.\nIterations: 
#{iterations.inspect}"
-----

catch/throw don't need to be used often, but when they are needed, they work 
great for all of the same thing that labeled loops in Perl work for, and then 
some.


Kirk Haines