From: Brian Candler <b.candler@...>
Date: 2008-11-03T22:23:05+09:00
Subject: Re: RubyMacros 0.1.0 Released

Caleb Clausen wrote:
> A recently requested new feature on ruby-core was __DIR__, which acts
> like __FILE__, but returns the directory containing the current source
> file. As a macro, that is:
> 
> macro __DIR__
>   :( File.dirname __FILE__ )
> end
> 
> Now maybe (now that I've seen your block-as-binding trick) you can
> actually write this as a method, something like,
> 
> def __DIR__(&ctx)
>   File.dirname(eval("__FILE__",ctx))
> end
> 
> I have no ruby ATM, and can't check if that works or not, sorry.

It seems to, as long you provide a dummy block: __DIR__{}.

I think there's a simpler solution though:

  def __DIR__
    # filename:nnn[:in `method']
    File.dirname(caller.first.split(':').first)
  end

Actually, it's a pain that 'caller' doesn't provide a proper composite 
object with filename, line number, method name. Windows people may have 
C:... at the front of their filename. A regexp split should fix that.
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