Compilare: user.cpp: In function ‘double area(const std::vector<point>&)’: user.cpp:36:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < points.size(); ++ i) ^ user.cpp: In function ‘void rewind(std::vector<point>&, const point&)’: user.cpp:81:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < points.size(); ++ i) ^ user.cpp:83:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = i; j < points.size(); ++ j) ^ user.cpp: In function ‘int main()’: user.cpp:112:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < points.size(); ++ i) ^