# File lib/facet/array/at_rand.rb, line 77
  def at_rand!(number=nil)
    unless number
      return delete_at( rand_index )
    else
      number = number.to_int
      all = (0...size).to_a
      idx = rand_index(number)
      vals = values_at(*idx)
      replace( values_at( *(all - idx) ) )
      return vals    
    end
  end