func_code: def search(ls, letter):
      if ls == []:
          return False
      elif ls[0] == val:
          return True
      else:
          return search(ls[1:], val)
  
  
  def index(ls, letter):
      if ls == []:
          return -1
      elif ls[0] == val:
          return val
      else:
          return search(ls[1:], val)