From: "Brian Schröder" <ruby@...>
Date: 2004-11-10T06:51:50+09:00
Subject: Re: Iterating trough hash

On Wed, 10 Nov 2004 06:41:08 +0900
Michael DeHaan <michael.dehaan@gmail.com> wrote:

> Hmm, that's not a good bug there, so I'll pull the "history" thing out
> (I was trying to be too clever)...
> 
> module Enumerable
>  def each_permutation
>    each do |item1|
>      each do |item2|
>          yield [item1,item2] unless (item1 === item2)
>      end
>    end
>  end
> end
> 
> 

Hello Michael,

I think, that this is not each_permutation, but each_ordered_pair_of_elements_in_the_set_except_for_equal_elements.

each_permutation would be all shuffles of the original enumerable.

And it is not what the OP wanted, as he wanted all unordered pairs. So maybe

module Enumerable
 def each_self_pair
   each do |item1|
     each do |item2|
         yield [item1,item2]
     end
   end
 end
end

{'me' => 1, 'you' => 1, 'him' => 1}.each_self_pair do | ((p1, a1), (p2, a2) |
  next if p1 <= p2 
  puts "#{p1} and #{p2} with age #{a1 + a2}"
end

would be more appropriate.

Regards,

Brian 

> 
> 
> [snip]

-- 
Brian Schr�der
http://www.brian-schroeder.de/