From: David Alan Black <dblack@...>
Date: 2002-02-11T23:23:08+09:00
Subject: Re: array diff

Hi --

On Mon, 11 Feb 2002, Tobias Reif wrote:

> Florian,
>
> thanks to Hugh, I realized that
>
> class Array
>    def minus other
>      out = self.dup
>      other.each do |el|
>        if out.index(el)
>          out.delete_at out.index(el)
>        end
>      end
>      out
>    end
> end
>
> is better.

But didn't you want:

  [1,1].minus([1,1,1]) => [1]

?

If so, you'd have to differentiate the arrays based on size:

  class Array
     def minus other
       (long,short) = [self,other].max.dup, [self,other].min
       short.each do |el|
	 if long.index(el)
	   long.delete_at long.index(el)
	 end
       end
       long
     end
  end

(Mind you, I think the #delete_at could get slow with big arrays,
since it's rewriting the array so often.)


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav