# File lib/facets/core/enumerable/each_combination.rb, line 18
  def each_combination(k=2)
    s = self.to_a
    n = s.size
    return unless (1..n) === k
    idx = (0...k).to_a
    loop do
      yield s.values_at(*idx)
      i = k - 1
      i -= 1 while idx[i] == n - k + i
      break if i < 0
      idx[i] += 1
      (i + 1 ... k).each {|j| idx[j] = idx[i] + j - i}
    end
  end