/in/foo.cc: In member function 'int PolyListArray::Sum()':
/in/foo.cc:78:13: error: invalid initialization of non-const reference of type 'PolyList&' from an rvalue of type 'PolyList'
    tem=(tem + p[i]);
        ~~~~~^~~~~~~
/in/foo.cc:30:11: note:   initializing argument 1 of 'PolyList PolyList::operator=(PolyList&)'
  PolyList operator = (PolyList & p)
           ^~~~~~~~