View Compilation Error

0_0_19737345_8994.cpp: In function 'void clear77(STACKINT)':
0_0_19737345_8994.cpp:25:12: error: cannot convert 'std::stack<_Tp, _Sequence>::empty<int, std::deque<int, std::allocator<int> > >' from type 'bool (std::stack<int>::)() const' to type 'bool'
  while (!x.empty) {
            ^
0_0_19737345_8994.cpp:25:12: error: in argument to unary !