Compilare: user.cpp: In function ‘long int s2i(std::string)’: user.cpp:8:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ^ user.cpp: In function ‘long int eval(std::string)’: user.cpp:16:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ^ user.cpp:29:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ^