From: Dan Doel <djd15@...>
Date: 2004-04-20T05:32:22+09:00
Subject: Re: convert yield to proc

The original problem with the code was that he was instance_evaling the
block in #mode. So if no block was passed, he'd end up with something like
the following:

  instance_eval do
    yield
  end

And you can't yield in a block given to instance eval (not sure I totally
understand why, but I have a gut feeling that you shouldn't try it :)).

Using an & parameter wraps the given block in a Proc. If no block is given,
it's nil. If you call yield in a block, it will yield to the block given to
the enclosing method.

Hope this helps.

- Dan