Compilare: user.cpp: In function ‘std::ostream& operator<<(std::ostream&, ArboreAVL&)’: user.cpp:90:5: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘std::istream& operator>>(std::istream&, ArboreAVL&)’: user.cpp:101:5: warning: no return statement in function returning non-void [-Wreturn-type] } ^