input: Write a function to check if a given string has matching parentheses. The function should return True if the string has matching parentheses, otherwise return False. If the input string is empty, the function should return True.
  assert matching_paren("(a+b)") == True
  assert matching_paren("(a+b))") == False
  assert matching_paren("((a+b)") == False
  assert matching_paren("a+b") == True
  assert matching_paren("") == True
output: def matching_paren(s):
      stack = []
      for char in s:
          if char == '(':
              stack.append(char)
          elif char == ')':
              if not stack:
                  return False
              stack.pop()
      return len(stack) == 0