Calculate 2^n that is computable even where n is larger than ULONG_LONG_MAX.

culc_power_of_2.rb

factor = 65536

cy_pos = 0
cy_interval_list = Array.new
next_cy_interval_list = Array.new
cy_interval_count = 0

digit = 1
num_of_digit = 1
is_cy = false
num_str = String.new
begin
  factor_this_digit = factor - cy_pos
  puts "rest: #{factor_this_digit}\n"
  cy_interval = cy_interval_list.shift
  is_cy = false
  factor_this_digit.times do |num|
    num_of_digit *= 2
    if not cy_interval.nil?
      cy_interval -= 1
      if cy_interval == 0
        num_of_digit += 1
        cy_interval = cy_interval_list.shift
      end
    end
    cy_interval_count += 1
    if num_of_digit >= 10
      num_of_digit %= 10
      if not is_cy
        cy_pos += num + 1
        is_cy = true
      else
        next_cy_interval_list << cy_interval_count
      end
      cy_interval_count = 0
    end
  end 
  num_str = num_of_digit.to_s + num_str

  # swap
  temp = cy_interval_list
  cy_interval_list = next_cy_interval_list
  next_cy_interval_list = temp
  
  next_cy_interval_list.clear
  num_of_digit = 1
  digit += 1
end while is_cy

puts "#{num_str}\n"