An Alternative (and preferred) wording for the has methods

array.rb

# all_in, any_in, and none_in extension to Array.
#
class Array

  # Returns true if the argument list contain every item of the array.
  #
  # Basic Usage:
  #
  #   [:black, :blue].all_in :black, :blue          # => true
  #   [:black].all_in :black, :red                  # => true
  #   [:black, :blue].all_in :black, :red, :blue    # => false
  #
  def all_in(*ary)
    reduce(true) { |memo, obj| memo && ary.include?(obj) }
  end

  # Returns true if the argument list contains one or more items from the array .
  #
  # Basic Usage:
  #
  #   [:black, :blue].any_in :black                 # => true
  #   [:black, :blue].any_in :black, :red           # => true
  #   [:black, :blue].any_in :green, :red           # => false
  #
  def any_in(*ary)
    reduce { |memo, obj| memo || ary.include?(obj) }
  end

  # Return true is the the argument list has no items in common with the array. (Opsitie of any_in)
  #
  #   [:black, :blue].none_in :black                 # => false
  #   [:black, :blue].none_in :black, :red           # => false
  #   [:black, :blue].none_in :green, :red           # => true
  #
  def none_in(*ary)
    !any_in(*ary)
  end

end