foo.cc: In member function ‘PolyList PolyList::operator+(const PolyList&)’:
foo.cc:28:35: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<PolyListNode>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   28 |                 for (int i = 0; i < poly.size(); i++)
      |                                 ~~^~~~~~~~~~~~~
foo.cc:30:35: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<PolyListNode>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   30 |                 for (int i = 0; i < p.poly.size(); i++)
      |                                 ~~^~~~~~~~~~~~~~~
foo.cc: In function ‘int main()’:
foo.cc:47:27: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<PolyListNode>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   47 |         for (int i = 0; i < Pc.poly.size(); i++)
      |                         ~~^~~~~~~~~~~~~~~~