View Compilation Error

0_0_36780463_15216.cpp:92:25: error: 'function' has not been declared
   void traverse(int id, function<void(int)> func) {
                         ^
0_0_36780463_15216.cpp:92:33: error: expected ',' or '...' before '<' token
   void traverse(int id, function<void(int)> func) {
                                 ^
0_0_36780463_15216.cpp: In member function 'void Treap<Key>::traverse(int, int)':
0_0_36780463_15216.cpp:94:23: error: 'func' was not declared in this scope
     traverse(lft[id], func); func(id); traverse(rit[id], func);
                       ^