Compilare: main.cpp: In member function 'int Polygon::area()': main.cpp:69:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0 ; i < points.size() - 1 ; ++ i) { ~~^~~~~~~~~~~~~~~~~~~ main.cpp: In function 'int main(int, const char**)': main.cpp:99:12: warning: 'right' may be used uninitialized in this function [-Wmaybe-uninitialized] int left, right ; ^~~~~ main.cpp:119:25: warning: 'left' may be used uninitialized in this function [-Wmaybe-uninitialized] out << right - left << '\n' ; ^~~~