bind包装器

调用bind的一般形式：auto newCallable = bind(callable,arg_list);

其中，newCallable本身是一个可调用对象，arg_list是一个逗号分隔的参数列表，对应给定的 callable的参数。

当我们调用newCallable时，newCallable会调用callable,并传给它arg_list中 的参数。

bind的使用

#include<iostream>
#include<functional>
using namespace std;int Add(int a, int b)
{cout << a << "  " << b << endl;return a + b;
}class Sub
{
public:int sub(int a, int b){cout << a << "  " << b << endl;return a - b;}double mul(int a, int b, double rate){return a * b * rate;}static int test(int a, int b){return a + b;}
};int main(void)
{function<int(int, int)>func1 = bind(Add, placeholders::_1, placeholders::_2);function<int(int, int)>func2 = bind(Add, placeholders::_2, placeholders::_1);func1(1, 2);func1(2, 1);function<int(int, int)>func3 = bind(&Sub::sub,Sub(), placeholders::_1, placeholders::_2);function<int(int, int)>func4 = bind(&Sub::sub,Sub(), placeholders::_2, placeholders::_1);func3(5, 6);func4(5, 6);function<int(int, int)>func5 = bind(&Sub::mul, Sub(), placeholders::_1, placeholders::_2, 1.5);function<double(int, int)>func6 = bind(&Sub::mul, Sub(), placeholders::_1, placeholders::_2, 1.5);cout << func6(3,3)<<endl;function<int(int, int)>func7 = bind(&Sub::test, placeholders::_1, placeholders::_2);cout << func7(10, 20)<<endl;return 0;
}