Compilare: user.cpp: In function ‘int test_up_to(int)’: user.cpp:98:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:111:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < string_number.size(); ++j) ^ user.cpp:115:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < string_number.size(); ++j) ^