C等效于C#的Func

public double Average<T>(IList<T> items,Func<T,double> selector)
{
    double average = 0.0;

    for (int i = 0; i < items.Count; i++)
    {
        average += selector(items[i])
    }

    return average / items.Count;
}

我可以用lambda表达式来调用它：

double average = Average(items,p => p.PropertyName);

我该怎么办？这是我到目前为止

template <typename T>
double average(const vector<T>& items,?)
{
    double average= 0.0;

    for (int i = 0; i < items.size(); i++)
    {
        average += ?;
    }

    return average/ items.size();
}

我怎么可以用c lambda来调用？

编辑：非常感谢,这里是我最终的结论：

template <typename T>
double average(const vector<T>& items,function<double(T)> selector)
{
    double result = 0.0;

    for (auto i = items.begin(); i != items.end(); i++)
    {
        result += selector(*i);
    }

    return result / items.size();
}

在main()中：

zombie z1;
z1.hit_points = 10;

zombie z2;
z2.hit_points = 5;

items.push_back(z1);
items.push_back(z2);

double average = average<zombie>(items,[](const zombie& z) {       
    return z.hit_points;
});