# File lib/facets/core/hash/op_add.rb, line 14
  def -(other)
    h = self.dup
    if other.respond_to?(:to_ary)
      other.to_ary.each do |k|
        h.delete(k)
      end
    else
      other.each do |k,v|
        if h.key?(k)
          h.delete(k) if value == h[k]
        end
      end
    end
  end