text: ## An example of a turing enumerator that enumerates
  ## strings in lexographic order
  
  def evenzeros_test(s):
      zeros = 0
      for c in s:
          if c == "0":
              zeros += 1
      return zeros%2 == 0
  
  
  N = 20
  s = "0"
  k = 1
  i = 0
  while i < N:
      if evenzeros_test(s):
          print(s)
          i += 1
      b = int(s, 2)
      b += 1
      s2 = format(b, 'b')
      if len(s2) > len(s):
          k += 1
          s = "0"*k
      else:
          s = s2
          if len(s) < k:
              s = "0"*(k-len(s)) + s