rb:6:in `<class:Parser>': uninitialized constant Parser::Printer (NameError) from parse_energy_data.rb:5:in `<main>'

gistfile1.rb

#/usr/bin/env ruby -w
#Usage parse <argument>
require 'csv'

class Parser
  include Printer
  attr_accessor :statistics

  def initialize filename
    self.statistics = {}
    deserialize_users filename
    print_statistics
  end

  def deserialize_users filename
    CSV.foreach(filename, col_sep: "|", headers: true) do |row|
      calculate_statistics(row)
    end 
  end

  private

  def calculate_statistics row
    statistics[:nbr_of_readings] += 1 
    statistics[:list_of_unique_customers] = []
    if !list_of_unique_customers.includes?(:cust_id)
      statistics[:list_of_unique_customers] << row[:cust_id]
      statistics[:nbr_of_unique_customers] += 1
    end

    statistics[:nbr_customers_with_electricity]  += 1 if row[:elect_or_gas] == 1
    statistics[:nbr_customers_with_gas]  += 1 if row[:elect_or_gas] == 2

    avg_consumption_month row[:bill_month]
  end

  def avg_consumption_month month 
    statistics[:"avg_consumption_#{month}"] += row[:consumption] 
    statistics[:"nbr_of_#{month}_bill_month"] += 1
    statistics[:"avg_consumption_#{month}"] /=  statistics[:"nbr_of_#{month}_bill_month"]
    statistics[:avg_total_consumption] += statistics[:"avg_consumption_#{month}"]
    statistics[:nbr_of_total_bill_month] += 1
    statistics[:avg_total_consumption] /= statistics[:nbr_of_total_bill_month]
  end

end

module Printer

  def print_statistics
    puts "number of readings: #{statistics[:nbr_of_readings]}"

    [:nbr_of_unique_customers, :nbr_customers_with_electricity, :nbr_customers_with_gas].each do |meth|
      puts "number of #{meth.to_s.humanize}: #{statistics[meth] }"
    end

    puts "AVERAGE CONSUMPTIONS".center(26,"-")
    Date::MONTHNAMES.compact.each do |month|
      puts "%10s %10d" %  ["month (all years)", statistics[:"avg_consumption_#{month.downcase}"]]
    end

  end
end

Parser.new argv[0]