c++ 输出单链表元素

Question

//函数声明部分friend ostream& operator<<<>(ostream&,SinglyList<T>&);    //输出单链表所有元素//函数定义template <class T>ostream& operator<<<>(ostream &out,SinglyList<T> &list){  out<<"(";  for(Node<T> *next=list.head->next; next != NULL; next = next->next)    {      out<<next->data;      if(next->next != NULL)    out<<",";    }  out<<")\n";  return out;}g++ 编译时报错：SinglyList.h:64:55: 错误：模板标识符‘operator<< <>’出现在基本模板的声明中 ostream& operator<<<>(ostream &out,SinglyList<T> &list)SinglyList.h:20:19: 错误：‘std::ostream& operator<<(std::ostream&, SinglyList<Computer>&)’的模板标识符‘operator<< <>’不匹配任何模板声明   friend ostream& operator<<<>(ostream&,SinglyList<T>&);    //输出单链表所有元素 这是我在书上看到的代码，在我的环境中编译报错。首先对于“operator<<<>”这部分中的<>不明白代表什么意思？先谢了。