Compilare: user.cpp: In function ‘int evalexp()’: user.cpp:36:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < s.size(); i ++){ ^ user.cpp: In function ‘int main()’: user.cpp:68:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++){ ^ user.cpp:65:12: warning: unused variable ‘y’ [-Wunused-variable] char x,y; ^