lambda，std::function, 函数对象,bind的使用备忘

Demo备忘，占坑

#include <iostream>
#include <functional>
#include <vector>
using namespace std;
using namespace std::placeholders;

const static int T_NUM = 10;

bool test_functional(const std::function<bool(int)> &f, int t) {
	return f(t);
}

struct test_struct
{
	public:
		bool operator()(int t) {
			if (t > T_NUM) {
				buffer.push_back(t);
			}
			return true;
		}

	public:
		std::vector<int> buffer;
};

int test_binder_functional(int a, int b) {
	return a+b;
}

int test_binder_function2(int &a) {
	return ++a;
}

class BindTestClass 
{
	public:
		BindTestClass(std::string name="") : name_(name) {}
		void Print(std::string prefix="") { std::cout << prefix << " " << name_ << std::endl;}
	private:
		std::string name_ {""};
};

int main()
{
	//函数对象
	test_struct t;
	test_functional(t,9);
	test_functional(t,10);
	test_functional(t,11);
	test_functional(t,12);
	//打印不出任何东西，函数对象到 std::function存在隐式转换
	for(auto it=t.buffer.begin(); it != t.buffer.end(); it++) {
		std::cout << *it << std::endl;
	}

	//-------------------------------
	// lambda
	std::vector<int> buffer;
	std::function<bool(int)> test_f = [&buffer](int t)->bool {
		if (t > T_NUM) {
			buffer.push_back(t);
		}  
	};

	test_functional(test_f,9);
	test_functional(test_f,10);
	test_functional(test_f,11);
	test_functional(test_f,12);
	// 打印 11,12
	for(auto it=buffer.begin(); it != buffer.end(); it++) {
		std::cout << *it << std::endl; 
	} 

	//--------------------------------
  // bind的使用
	// bind 固定某个参数
	auto bind_test_f = std::bind(test_binder_functional,_1,10);
	std::cout << bind_test_f(10) << std::endl;

	// bind
	auto divide_f = std::bind(std::divides<double>(), _1, 7);
	std::cout << divide_f(49) << std::endl;

	// nesting bind 嵌套bind
	auto time3_f = std::bind(std::multiplies<double>(), _1, std::bind(std::multiplies<double>(),_1,_1));
	std::cout << time3_f(10) << std::endl;
	std::cout << time3_f(20) << std::endl;

	// bind_num_v will not change  引用bind需要加 ref 修饰
	int bind_num_v = 10;
	auto bind_num_f = std::bind(test_binder_function2,bind_num_v);
	bind_num_f();
	std::cout << bind_num_v << std::endl; 

	// bind_num_v will change  
	auto bind_num_f_c = std::bind(test_binder_function2,ref(bind_num_v));
	bind_num_f_c(); 
	std::cout << bind_num_v << std::endl;

	// bind class function 绑定类成员函数
	auto class_bind_f = std::bind(&BindTestClass::Print, _1, "my name is：");
	BindTestClass bindc("nicolas");
	class_bind_f(bindc);

	return 0;
}