Compilare: user.cpp: In function ‘std::istream& operator>>(std::istream&, bigint&)’: user.cpp:17:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();i++) ^ user.cpp: In function ‘std::ostream& operator<<(std::ostream&, bigint&)’: user.cpp:38:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i!=x.size()-1) ^ user.cpp: In function ‘bigint operator-(const bigint&, const int&)’: user.cpp:52:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<x.size()) ^ user.cpp: In function ‘bigint operator+(const bigint&, const int&)’: user.cpp:74:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<x.size()) ^ user.cpp: In function ‘bigint operator*(const bigint&, const bigint&)’: user.cpp:94:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<x.size();i++) ^ user.cpp:95:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0;j<y.size();j++) ^ user.cpp:97:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<c.size();i++) ^