Swap Elements Of An Array In Ruby

class Array
    def swap!(a,b)
         self[a], self[b] = self[b], self[a]
    self
    end
end

You can now do stuff like..

[1,2,3,4].swap!(2,3)  # = [1,2,4,3] etc..

Many thanks to Sam Stephenson and technoweenie for their suggestions.