From: John Pritchard-williams <monojohnny@...>
Date: 2008-08-29T06:15:27+09:00
Subject: Re: Subtle bug with catch/throw. Am I missing something?

Patrick Li wrote:
> Thanks for your responses.
> 
> I think I understand now. I was just using the catch as a lazy way to 
> break out of the loop. I can just use a loop flag instead then.
> 
> I still don't know why the "puts" statement avoids the error. The "do" 
> after the "while" doesn't help either.

Patrick,

Again total guesswork , but based on the other posts from people who 
actually know what they are talking about... - sounds like the symbol 
':exit' is possibly out-of-scope by the time the 'throw' is executed.

So (purely out of interest, as you are solving this another way...)

Could you try replacing :exit with an instance or class-based variable 
like:

def initialize
  @exit=:exit
end

And then refer to it in both your catch and throw ? (or at least your 
catch..)

Again, based on what's been posted here - sounds like timing plays a 
role here: maybe the 'puts' delays execution just-enough to keep the 
thread-of-execution within the method for the 'throw' to find the 
referring catch...?

This is quite an interesting problem...I'm learning quite a bit about 
ruby just from watching the other posts ! :)

Cheers

John


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