gistfile1.txt

class Range
  def oscillate(num_times: 1)

    previous_value = nil

    num_times.times do |index|
      first.upto(last) do |value|
        #protect against repeat values, since 
        #each oscillation directions don't know
        #about the other, and will otherwise
        #redundantly output the limit values
        yield value unless (value === previous_value)
        previous_value = value
      end

      last.downto(first) do |value|
        yield value unless (value === previous_value)
        previous_value = value
      end
    end
  end
end

(1..5).oscillate(num_times: 2) {|val| puts "val is #{val}"}