From: matz@... (Yukihiro Matsumoto)
Date: 2004-07-24T15:01:10+09:00
Subject: Re: Bug? String interpolation and continuations

Hi,

In message "Bug? String interpolation and continuations"
    on 04/07/22, Sam McCall <tunah.usenet@tunah.net> writes:

|The following gives me weird results:
|(Typed into IRB. The results are similar in ruby but because of the 
|simple example you get an infinite loop)

It's not a bug.  It's a feature.

|# Allow a continuation to escape
|store_cont = proc {|cont| $cont=cont; nil}
|
|puts "[#{callcc &store_cont}]"
|# prints '[]', as expected

saves the continuation to $cont, then evaluate "[#{nil}]".

|$cont.call("hello")
|# prints '[]hello]hello]hello]...'
|# expected '[hello]'

By calling the continuation the execution goes back to the saved
point, but no other states are restored, so that the value of
generating string (referenced from the local variable) remains the
last generated value after the jump.  Then execution concatenate
"hello", then "]".  Repeat forever.

That's what happened.

							matz.