From: "Thomas B." <tpreal@...>
Date: 2008-08-29T04:43:45+09:00
Subject: Re: Subtle bug with catch/throw. Am I missing something?

Patrick Li wrote:
>         @enterEvent.listen do
>           @state = method(:active)
>           puts "player entered"
>           throw :exit                     <-- Throw :exit
>         end

What does this @enterEvent.listen do? If it saves the block passed to it 
and terminates, and the block gets executed later, when the main control 
is already out of your idle method, you will get the error. Here's 
example of an error-producing code to illustrate what I say:

class K
  def listen(&b)
    @b=b
  end
  def idle
    catch(:a){listen{throw(:a)}}
  end
  def call
    @b.call
  end
end
k=K::new
k.idle
k.call

It causes an error even though throw is inside catch, when we look at 
the code.

TPR.
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