From: Gavin Kistner <gavin@...>
Date: 2004-07-14T00:08:37+09:00
Subject: Re: Ruby quickies and useful idioms

On Jul 12, 2004, at 1:47 AM, Martin DeMello wrote:
> I've found this useful on several occasions
>
> class Array
>   include EnumerableOperator
>   def all_pairs
>     a = size-1
>     for i,j in product(0..a, 0..a, proc {|i,j| i < j})
>       yield at(i), at(j)
>     end
>   end
> end

It's too early in the morning for me to decode this. Is this the same 
as my Array#each_unique_pair method documented here:

http://phrogz.net/RubyLibs/rdoc/classes/Array.html#M000061

If so, the implementation which doesn't require anything else is simply:

class Array
         def each_unique_pair
                 self.each_with_index{ |a,i|
                         self[(i+1)..-1].each{ |b| yield a,b }
                 }
         end
end