create array of ranges from array of individual values

to_range.rb

require 'pp'
require 'date'



def to_range  low, high, input, output
  if high > input.length
    return output.each_slice(2).map {|a| a }.map { |x| x[0]..x[1]}
  end
  if low == 0
    output = Array.new
    output << input[low]
  else
    if input[low]+1 != input[high]
      output << input[low]  
      output << input[high] if input[high] 
    end
  end
  to_range  (low+1), (high+1), input, output
end


input = [1,2,3,4,5,100,101,102,400,401,402,403,404,405,406]
pp to_range  0, 1, input, nil    # => [1..5, 100..102, 400..406]