Compilare: user.cpp: In function ‘bool match(const number&, const number&)’: user.cpp:33:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i(0) ; i < a.size() ; ++i) ^ user.cpp: In function ‘void add(number&, number)’: user.cpp:56:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0 ; i < a.size() ; ++i) ^ user.cpp:61:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0 ; i < b.size() ; ++i) ^