typedef  void（*ptr）（int，int）// 這里的ptr就是一個函數(shù)指針

std::function<void(int ,int)> func;

    #include <iostream>  
    #include <vector>  
    #include <list>  
    #include <map>  
    #include <set>  
    #include <string>  
    #include <algorithm>  
    #include <functional>  
    #include <memory>  
    using namespace std;  
    //聲明一個模板  
    typedef std::function<int(int)> Functional;  
    //normal function  
    int TestFunc(int a)  
    {  
        return a;  
    }  
    //lambda expression  
    auto lambda = [](int a)->int{return a;};  
    //functor仿函數(shù)  
    class Functor  
    {  
    public:  
        int operator() (int a)  
        {  
            return a;  
        }  
    };  
    //類的成員函數(shù)和類的靜態(tài)成員函數(shù)  
    class CTest  
    {  
    public:  
        int Func(int a)  
        {  
            return a;  
        }  
        static int SFunc(int a)  
        {  
            return a;  
        }  
    };  
    int main(int argc, char* argv[])  
    {  
        //封裝普通函數(shù)  
        Functional obj = TestFunc;  
        int res = obj(0);  
        cout << "normal function : " << res << endl;  
        //封裝lambda表達式  
        obj = lambda;  
        res = obj(1);  
        cout << "lambda expression : " << res << endl;  
        //封裝仿函數(shù)  
        Functor functorObj;  
        obj = functorObj;  
        res = obj(2);  
        cout << "functor : " << res << endl;  
        //封裝類的成員函數(shù)和static成員函數(shù)  
        CTest t;  
        obj = std::bind(&CTest::Func, &t, std::placeholders::_1);  
        res = obj(3);  
        cout << "member function : " << res << endl;  
        obj = CTest::SFunc;  
        res = obj(4);  
        cout << "static member function : " << res << endl;  
        return 0;  
    }  

 double my_divide(double x, double y) { return x / y; };
 int main(int argc, char* argv[])
 {
	 auto fn_half = std::bind(my_divide, std::placeholders::_1, 2);
	 std::cout << fn_half(10) << '\n';                        // 輸出為5
	 return 0;
}