有关下面C++代码的说法，错误的是（ ）。
#include <iostream>using namespace std; class MoreData { int * __data; int head, tail, capacity;public: MoreData(int cap) { capacity = cap; __data = new int[capacity]; head = tail = 0; } MoreData & push(int val) { __data[tail++] = val; return *this; } int pop() { return __data[head++]; } int size() { return tail - head; }};int main() { auto myData = MoreData(100); myData.push(1); myData.push(2); myData.push(3); myData.push(11).push(12).push(13); cout << myData.pop() << endl; return 0;}