Compilare: user.cpp: In function ‘int evalexp()’: user.cpp:38:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < s.size(); i ++){ ^ user.cpp:53:27: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if(s[i] >= 'A' && s[i] <= 'Z' || (s[i] == 't' || s[i] == 'f')){ ^ user.cpp: In function ‘int main()’: user.cpp:70:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++){ ^ user.cpp:67:12: warning: unused variable ‘y’ [-Wunused-variable] char x,y; ^