From: Robert Klemme <bob.news@...>
Date: 2003-06-03T17:10:33+09:00
Subject: Re: Dynamically scoped variables


"Tanaka Akira" <akr@m17n.org> schrieb im Newsbeitrag
news:87k7c3mxma.fsf@serein.a02.aist.go.jp...
> 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

Very nice indeed!  Couldn't we save one lookup by doing

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

Regards

    robert