# returns an enumerator which executes block on each nth iteration
def on_nth_run_enum freq, &block
  Enumerator.new do |yielder|
    loop do
      freq.times do
        yielder.yield
      end
      block.call
    end
  end
end
 
# an object of this class will execute given block
# every nth time "run" method has been invoked
class OccasionalRunner
  def initialize freq, &block
    @freq = freq
    @block = block
    @counter = 0
  end
 
  def run
    @counter = (@counter + 1) % @freq
    @block.call if @counter == 0
  end
end
 
# returns lamda which will execute given block
# every nth time being called
def on_nth_run_fun freq, &block
  counter = 0
  -> {
    counter = (counter + 1) % freq
    block.call if counter == 0
  }
end
 
janitor_enum = on_nth_run_enum 3 do
  puts 'cleanup - enumerable way'
end
 
janitor_oo = OccasionalRunner.new 3 do
  puts 'cleanup - OO way'
end
 
janitor_fun = on_nth_run_fun 3 do
  puts 'cleanup - functional style'
end
 
(1..10).each do |i|
  puts i
  janitor_enum.next
  janitor_oo.run
  janitor_fun.call
end

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