foo.cc: In member function 'PolyLinkList& PolyLinkList::operator=(const PolyLinkList&)':
foo.cc:108:13: warning: right operand of comma operator has no effect [-Wunused-value]
  108 |   delete p,t;
      |             ^
foo.cc: In member function 'PolyLinkList PolyLinkList::operator+(PolyLinkList&)':
foo.cc:139:13: warning: right operand of comma operator has no effect [-Wunused-value]
  139 |   delete p,q;
      |             ^
foo.cc: In function 'int main()':
foo.cc:183:18: warning: unused variable 'x' [-Wunused-variable]
  183 |  int n,coe,index,x;
      |                  ^

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