class Unparser::Equalizer

def define_cmp_method
  keys = @keys
  define_method(:cmp?) do |comparator, other|
    keys.all? do |key|
      __send__(key).public_send(comparator, other.__send__(key))
    end
  end
  private :cmp?
end

def define_hash_method
  keys = @keys
  define_method(:hash) do
    keys.map(&public_method(:__send__)).push(self.class).hash
  end
end

def define_inspect_method
  keys = @keys
  define_method(:inspect) do
    klass = self.class
    name  = klass.name || klass.inspect
    "#<#{name}#{keys.map { |key| " #{key}=#{__send__(key).inspect}" }.join}>"
  end
end

def define_methods
  define_cmp_method
  define_hash_method
  define_inspect_method
end

def included(descendant)
  descendant.include(Methods)
end

def initialize(*keys)
  @keys = keys
  define_methods
  freeze
end