func_code: def search(str, letter):
      i = 0
      while i < len(str):
          if str[i] == letter:
              return True
          i = i + 1
      return False
  
  
  def index(str, letter, pos):
      if pos == len(str):
          return False
      elif str[pos] == letter:
          return True
      else:
          return search(str, letter, pos)