Compilare: user.cpp: In function ‘int eval_not()’: user.cpp:63:9: warning: unused variable ‘r’ [-Wunused-variable] int r; ^ user.cpp: In function ‘int main()’: user.cpp:89:27: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if(st[i]<='Z' && st[i]>='A' || st[i]=='(' || st[i]==')') ^ user.cpp: In function ‘int eval()’: user.cpp:17:9: warning: ‘r’ may be used uninitialized in this function [-Wmaybe-uninitialized] int r; ^