From: gltewalt@... (illocutionist)
Date: 2004-07-23T06:07:00+09:00
Subject: Re: Bug? String interpolation and continuations

Carlos <angus@quovadis.com.ar> wrote in message news:<20040722102042.GA1575@quovadis.com.ar>...
> [Sam McCall <tunah.usenet@tunah.net>, 2004-07-22 08.52 CEST]
> > 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)
> > 
> > =================================
> > # Allow a continuation to escape
> > store_cont = proc {|cont| $cont=cont; nil}
> > 
> > puts "[#{callcc &store_cont}]"
> > # prints '[]', as expected
> > 
> > $cont.call("hello")
> > # prints '[]hello]'
> > # expected '[hello]'
> 
> My guess is, the line with the puts and the interpolated string is
> internally translated to something like:
> 
> s = "["
> s << callcc &store_cont
> s << "]"
> 
> puts s
> 
> --

This doesnt address your problem fully, but you can do:
puts "[#{callcc &store_cont}" + "]"
$cont.call("hello")
# [hello]
# => nil