Compilare: user.cpp: In function ‘bool eval_not()’: user.cpp:116:10: warning: unused variable ‘r’ [-Wunused-variable] bool r; ^ user.cpp: In function ‘int main()’: user.cpp:142:27: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if(st[i]<='Z' && st[i]>='A' || st[i]=='(' || st[i]==')') ^ user.cpp: In function ‘bool eval()’: user.cpp:93:1: warning: control reaches end of non-void function [-Wreturn-type] } ^