From: dblack@...
Date: 2005-12-14T00:43:31+09:00
Subject: Re: Array.invert

Hi --

On Tue, 13 Dec 2005, Christer Nilsson wrote:

> I would like to see invert "rubyfied".
> (Yes, I'm trying to get a grip of what this word means :-)

Aren't we all?  But the trying is so much fun :-)

Here's a version that might be more idiomatic, and that passes all
your tests:

class Array
   def invert
     res=[]
     each_with_index do |e,i|
       if e
         e.each do |f|
           (res[f] ||= []) << i
         end
       end
     end
     res
   end
end


David

-- 
David A. Black
dblack@wobblini.net

"Ruby for Rails", forthcoming from Manning Publications, April 2006!