Why this source code compiles error?

Question

#include <iostream>

using namespace std;

class Stack {

int *p = new int[num];

int num = 0;

public:

Stack& operator<<(int x);

void operator >> (int &x);

bool operator!();

};

bool Stack::operator!() {

if (num == 0) return true;

else return false;

}

Stack& Stack::operator<<(int x) {

num++;

p[num - 1] = x;

return *this;

}

void Stack::operator >> (int &x) {

x = p[num - 1];

num--;

}

int main() {

Stack stack;

stack << 3 << 5 << 10;

while (true) {

if (!stack) break;

Answer 1

Save your code on code playground section (that here seem is not full), copy his url and post here

Answer 2

please help me:(