/in/foo.cc:41:7: error: extra qualification 'LinkStack::' on member 'isEmpty' [-fpermissive]
  bool LinkStack::isEmpty()
       ^~~~~~~~~
/in/foo.cc:52:3: error: extra qualification 'SeqStack::' on member 'SeqStack' [-fpermissive]
   SeqStack::SeqStack()
   ^~~~~~~~
/in/foo.cc:57:2: error: extra qualification 'SeqStack::' on member 'SeqStack' [-fpermissive]
  SeqStack::~SeqStack()
  ^~~~~~~~
/in/foo.cc:61:7: error: extra qualification 'SeqStack::' on member 'push' [-fpermissive]
  void SeqStack::push(int x)
       ^~~~~~~~
/in/foo.cc:66:6: error: extra qualification 'SeqStack::' on member 'pop' [-fpermissive]
  int SeqStack::pop()
      ^~~~~~~~
/in/foo.cc:71:7: error: extra qualification 'SeqStack::' on member 'isEmpty' [-fpermissive]
  bool SeqStack::isEmpty()
       ^~~~~~~~