From: Tanaka Akira <akr@...17n.org>
Date: 2003-06-03T16:25:03+09:00
Subject: Re: Dynamically scoped variables

In article <3EDC224D.90803@pragprog.com>,
  Dave Thomas <dave@pragprog.com> writes:

> Just as a bit of fun I posted a piece on implementing dynamically scoped 
> variables in Ruby at
>
>     http://pragprog.com/pragdave/Tech/Random/StackContext.rdoc,v
>
> I'm sure there are easier ways. I just hacked this one out, so I'm happy 
> to be humiliated with better solutions.

def with_context(params)
  Thread.current[:dynamic] ||= []
  Thread.current[:dynamic].push params
  begin
    yield
  ensure
    Thread.current[:dynamic].pop
  end
end

def find_in_context(name)
  Thread.current[:dynamic].reverse_each {|params|
    return params[name] if params.has_key? name
  }
  raise "Can't find context value for #{name}"                                                                   
end
-- 
Tanaka Akira