Compilare: user.cpp: In function ‘char citeste(const string&, int)’: user.cpp:9:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] return (poz < str.size()) ? (poz < 0) ? 0 : str[poz]-'0' : 0; } ^ user.cpp: In function ‘void scrie(std::string&, int, int)’: user.cpp:12:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(str.size() <= poz){ ^ user.cpp: In function ‘void difference(const string&, const string&, std::string&)’: user.cpp:29:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0, in_minte = 0; i < mare.size(); ++i, in_minte /= 10){ ^ user.cpp: At global scope: user.cpp:87:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main(){ ^