C++模拟实现简易vector容器（模板类/命名空间/重载运算符）

参考了这篇博客：C++实现vector

练习模板类，命名空间，重载运算符的基础使用。加了个命名空间和对方括号的重载，使得可以通过索引访问数据。

#include 

namespace Morpheus {

    template
    class vector {
    private:
        T* _first;
        T* _last;
        T* _end;

    public:
        vector(int size = 5) {
            _first = new T[size];
            _last = _first;
            _end = _first + size;
        }
        ~vector() {
            delete _first;
            _first = nullptr;
            _last = nullptr;
            _end = nullptr;
        }
        bool isEmpty() {
            return _first == _last;
        }
        bool isFull() {
            return _last == _end;
        }
        int size() {
            return _last - _first;
        }
        void push_back(const T& x) {
            if (isFull()) {
                expand();
            }
            *_last++ = x;
        }
        void pop_back() {
            if (!isEmpty()) {
                _last--;
            }
        }
        T operator[](const int& i) {
            return _first[i];
        }

    private:
        void expand() {
            int len = _end - _first;
            T* temp = new T[2 * len];

            for (int i = 0; i < len; ++i) {
                temp[i] = _first[i];
            }

            delete[] _first;
            _first = temp;
            _last = _first + len;
            _end = _first + 2 * len;

        }
    };
}

int main() {
    Morpheus::vector v;
    v.push_back(1.2);
    v.push_back(1.3);
    v.push_back(1.4);
    for (int i = 0; i < v.size(); ++i) {
        std::cout << v[i] << ",";
    }
    v.pop_back();
    v.pop_back();
    for (int i = 0; i < v.size(); ++i) {
        std::cout << v[i] << ",";
    }
}