加速C++(第 3.2.1 节：矢量<double>作业)

在《Accelerated c++》第42页的3.2.1 -在vector中存储数据集合一节中，我在遵循它告诉我的输入后发现了代码中的一个错误。

// revised version of the excerpt
double x;
vector<double> homework;
// invariant: homework contains all the homework grades read so far
while (cin >> x)
    homework.push_back(x);

我理解向量的概念，但我就是不明白为什么我的代码会给我一个错误消息，特别是指向

vector<double> homework;

声明。c++ 11和c++ 14不再支持向量的这种声明了吗?

这是我的确切代码:

#include "stdafx.h"
#include <iomanip>
#include <iostream>
#include <ios>
#include <string>
using std::cin;         using std::string;
using std::cout;        using std::setprecision;
using std::endl;        using std::streamsize;
int main()
{
    // ask for and read the student's name
    cout << "n  Please enter your first name: ";
    string name;
    cin >> name;
    cout << "  Hello, " << name << "!" << endl;
    // ask for and read the midterm and final grades
    cout << "  Please enter your midterm and final exam grades: ";
    double midterm, final;
    cin >> midterm >> final;
    // ask for the homework grades
    cout << "  Enter all your homework grades, "
            "  followed by end-of-file: ";
    //the number and sum of grades read so far
    int count = 0;
    double sum = 0;
    // a variable into which to read
    double x;
    vector<double> homework;
    /*invariant:
    we have read COUNT grades so far, and
    SUM is the sum of the first COUNT grades*/
    while (cin >> x) {
        homework.pushback(x);
    }
    // write the result
    streamsize prec = cout.precision();
    cout << "  Your final grade is " << setprecision(3)
        << 0.2 * midterm + 0.4 * final + 0.4 * sum / count
        << setprecision(prec) << endl;
    return 0;
}