From: Stefan Kanev <stefan.kanev@...>
Date: 2009-01-30T00:10:59+09:00
Subject: Re: How can I get the arguments passed to the caller.

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And I have to override Array#each. I'll also need to override #map, #select
and so on. Not a good deal :(

On Tue, Jan 27, 2009 at 7:46 PM, Robert Klemme
<shortcutter@googlemail.com>wrote:

> 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
>
>

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