From: Robert Klemme <shortcutter@...>
Date: 2009-01-28T02:46:27+09:00
Subject: Re: How can I get the arguments passed to the caller.

2009/1/27 Stefan Kanev <stefan.kanev@gmail.com>:
> Thanks for the advice. I would have never had thought of something as
> straightforward as evaling 'local_variables' in the binding. Unfortunatelly,
> I believe that this doesn't yield the arguments if they are not named.
>
> I'm actually trying, out of curiosity, to implement a very straightforward
> idea:
>
>  %w{more chunky bacon}.each { puts it.length }
>
> Like, have *it* to actually be the 'implicit blog argument', not unlike
> perl's $_. Again, I'm doing that out of curiosity. Any ideas how I can
> accomplish it without touching the interpreter's C code? :)

IMHO you can't because the current value is only known by method
#each.  Wait, you could cook something up using thread local variables

18:41:58 tmp$ ./it.rb
4
6
5
18:42:41 tmp$ cat it.rb
#!/bin/env ruby

def it
  Thread.current[:each].last rescue nil
end

class Array
  alias _each each
  def each(&b)
    stack = Thread.current[:each] ||= []
    _each do |val|
      stack.push val
      begin
        b.call
      ensure
        stack.pop
      end
    end
  end
end

%w{more chunky bacon}.each { puts it.length }
18:42:42 tmp$

But note that you have to change *all* implementations of #each which
is difficult to achieve because classes can spring into existence all
the time. Alternatively write a global each which receives the
Enumerable as argument.

Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end