C++11中bind绑定器和function函数对象介绍

#include<iostream>
#include<vector>
#include<functional>
#include<algorithm>//泛型算法
#include<ctime>
using namespace std;
template<typename Container>
void showContainer(Container& con)
{
	//typename Container::iterator it=con.begin();
	auto it = con.begin();
	for (; it != con.end(); ++it)
	{
		cout << *it << " ";
	}
	cout << endl;
}
int main()
{
	vector<int> vec;
	srand(time(nullptr));
	for (int i = 0; i < 20; ++i)
	{
		vec.push_back(rand() % 100 + 1);
	}
	showContainer(vec);

	sort(vec.begin(), vec.end());//默认从小到大排序
	showContainer(vec);

	//greater需要二元函数对象
	sort(vec.begin(), vec.end(), greater<int>());//从大到小排序
	showContainer(vec);

	/*
	把70按顺序插入到vec容器中 ->找第一个小于70的数字
	operator()(const T &val)
	greater a>b
	less a<b
	绑定器+二元函数对象=》一元函数对象
	bind1st:+greater bool operator()(70,const_Ty&_Right)
	bind2nd:+less bool operator()(const_Ty &_Left,70)
	*/
	auto it1 = find_if(vec.begin(), vec.end(), bind1st(greater<int>(), 70));
	if (it1 != vec.end())
	{
		vec.insert(it1, 70);
	}
	showContainer(vec);
	return 0;
}

#include<iostream>
#include<vector>
#include<functional>
#include<algorithm>
#include<ctime>
using namespace std;
template<typename Container>
void showContainer(Container& con)
{
	auto it = con.begin();
	for (; it != con.end(); ++it)
	{
		cout << *it << " ";
	}
	cout << endl;
}
//遍历两个迭代器之间的元素，如果满足函数对象的运算，就返回当前的迭代器，如果都不满足就返回end
template<typename Iterator,typename Compare>
Iterator my_find_if(Iterator first, Iterator last, Compare comp)
{
	//这里传入的comp是封装好的一元函数对象
	for (; first != last; ++first)
	{
		if (comp(*first))//获取容器的一个元素
		{
			return first;
		}
	}
	return last;
}
template<typename Compare,typename T>
class _mybind1st//绑定器是函数对象的一个应用
{
public:
	//这里传入的comp是二元函数对象
	_mybind1st(Compare comp,T val)
		:_comp(comp),_val(val){}
	//通过重载operator()把二元函数对象封装为一元函数对象
	bool operator()(const T& second)
	{
		return _comp(_val, second);
	}
private:
	Compare _comp;
	T _val;
};
template<typename Compare,typename T>
_mybind1st<Compare, T> mybind1st(Compare comp, const T& val)
{
	//直接使用函数模板，好处是可以进行类型的推演
	//这里传入的comp是一个二元函数对象
	//通过二元函数对象构造一元函数对象
	//绑定器本身是一个函数对象，也就是重载了operator()
	return _mybind1st<Compare, T>(comp, val);
}
int main()
{
	vector<int> vec;
	srand(time(nullptr));
	for (int i = 0; i < 20; ++i)
	{
		vec.push_back(rand() % 100 + 1);
	}
	showContainer(vec);

	sort(vec.begin(), vec.end());//默认从小到大排序
	showContainer(vec);

	//greater需要二元函数对象
	sort(vec.begin(), vec.end(), greater<int>());//从大到小排序
	showContainer(vec);

	auto it1 = my_find_if(vec.begin(), vec.end(), mybind1st(greater<int>(), 70));
	if (it1 != vec.end())
	{
		vec.insert(it1, 70);
	}
	showContainer(vec);

	return 0;
}

#include<iostream>
using namespace std;
template<typename T>
class Vector
{
public:
	Vector() { cout << "call Vector template init" << endl; }
};
//对char*类型提供完全特例化版本
template<>
class Vector<char*>
{
public:
	Vector() { cout << "call Vector<char*> init" << endl; }
};
//对指针类型提供的部分特例化版本（部分：只知道是个指针，但是指针的类型是什么不知道）
template<typename Ty>
class Vector<Ty*>
{
public:
	Vector() { cout << "call Vector<Ty*> init" << endl; }
};
//指针函数指针(有返回值，有两个形参变量)提供的部分特例化
template<typename R,typename A1,typename A2>
class Vector<R(*)(A1, A2)>
{
public:
	Vector() { cout << "call Vector<R(*)(A1,A2)> init" << endl; }
};
//针对函数(有一个返回值，有两个形参变量)类型提供的部分特例化
template<typename R, typename A1, typename A2>
class Vector<R(A1, A2)>
{
public:
	Vector() { cout << "call Vector<R(A1,A2)> init" << endl; }
};
int sum(int a, int b) { return a + b; }
int main()
{
	Vector<int> vec1;
	Vector<char*> vec2;
	Vector<int*> vec3;
	Vector<int(*)(int, int)> vec4;
	Vector<int(int, int)> vec5;

	//注意区分函数类型和函数指针类型
	typedef int(*PFUNC1)(int, int);
	PFUNC1 pfunc1 = sum;
	cout << pfunc1(10, 20) << endl;

	typedef int PFUNC2(int, int);
	PFUNC2* pfunc2 = sum;
	cout << (*pfunc2)(10, 20) << endl;
	return 0;
}

#include<iostream>
#include<typeinfo>
using namespace std;
//T包含了所有大的类型
template<typename T>
void func(T a)
{
	cout << typeid(T).name() << endl;
}
int sum(int a, int b) { return a + b; }

//把所有形参类型都取出来
template<typename R, typename A1, typename A2>
void func2(R(*a)(A1, A2))
{
	cout << typeid(R).name() << endl;
	cout << typeid(A1).name() << endl;
	cout << typeid(A2).name() << endl;
}
template<typename R,typename T,typename A1,typename A2>
void func3(R(T::*a)(A1, A2))
{
	cout << typeid(R).name() << endl;
	cout << typeid(T).name() << endl;
	cout << typeid(A1).name() << endl;
	cout << typeid(A2).name() << endl;
}
class Test
{
public:
	int sum(int a, int b) { return a + b; }
};
int main()
{
	//func(10);//int
	//func("aaa");//const char *
	func(sum);
	func2(sum);
	func3(&Test::sum);
	return 0;
}

#include<iostream>
#include<functional>
using namespace std;
void hello1()
{
	cout << "hello world!" << endl;
}
void hello2(string str)
{
	cout << str << endl;
}
int sum(int a, int b)
{
	return a + b;
}
int main()
{
	//从function的模板定义处，看到希望用一个函数类型实例化function
	function<void()> func1 = hello1;
	func1();//func1.operator() => hello1()

	function<void(string)> func2 = hello2;
	func2("hello hello2!");

	function<int(int, int)> func3 = sum;
	cout << func3(2, 3) << endl;

	function<int(int, int)> func4 = [](int a, int b)->int {return a + b; };
	cout << func4(3, 4) << endl;
	return 0;
}

#include<iostream>
#include<functional>
using namespace std;

class Test
{
public://必须依赖一个对象void(Test::*pfunc)(string)
	void hello(string str) { cout << str << endl; }
};
int main()
{
	//成员方法一经编译都会多一个当前类型的this指针
	function<void (Test*, string)> func = &Test::hello;
	Test t;
	//对于成员方法的调用需要依赖一个成员对象
	func(&t, "call Test::hello!");
	return 0;
}

#include<iostream>
#include<functional>
#include<map>
using namespace std;
void doShowAllBooks(){ cout << "查看所有书籍信息" << endl; }
void doBorrow() { cout << "借书" << endl; }
void doBack() { cout << "还书" << endl; }
void doQueryBooks() { cout << "查询书籍" << endl; }
void doLoginOut() { cout << "注销" << endl; }
int main()
{
	int choice = 0;
	//使用function函数对象完成
	map<int, function<void()>> actionMap;
	actionMap.insert({ 1,doShowAllBooks });
	actionMap.insert({ 2,doBorrow });
	actionMap.insert({ 3,doBack });
	actionMap.insert({ 4,doQueryBooks });
	actionMap.insert({ 5,doLoginOut });
	for (;;)
	{
		cout << "------------------" << endl;
		cout << "1.查看所有书籍信息" << endl;
		cout << "2.借书" << endl;
		cout << "3.还书" << endl;
		cout << "4.查询书籍" << endl;
		cout << "5.注销" << endl;
		cout << "------------------" << endl;
		cout << "请选择：";
		cin >> choice;

		auto it = actionMap.find(choice);
		if (it == actionMap.end())
		{
			cout << "输入数字无效，重新选择" << endl;
		}
		else
		{
			it->second();
		}
		//不好，因为这块代码无法闭合，无法做到“开-闭”原则，也就是说这块代码随着需求的更改需要一直改，永远也闭合不了，避免不了要产生很多问题
		/*
		switch(choice)
		{
			case 1:break;
			case 2:break;
			case 3:break;
			case 4:break;
			case 5:break;
			default:break;
		}
		*/
	}
	return 0;
}

#include<iostream>
#include<functional>
using namespace std;

void hello(string str) { cout << str << endl; }
int sum(int a, int b) { return a + b; }

template<typename Fty>
class myfunction{};
/*
template<typename R,typename A1>
class myfunction<R(A1)>
{
public:
	//typedef R(*PFUNC)(A1);
	using PFUNC = R(*)(A1);
	myfunction(PFUNC pfunc):_pfunc(pfunc){}
	R operator()(A1 arg)
	{
		return _pfunc(arg);
	}
private:
	PFUNC _pfunc;
};

template<typename R, typename A1,typename A2>
class myfunction<R(A1,A2)>
{
public:
	//typedef R(*PFUNC)(A1);
	using PFUNC = R(*)(A1,A2);
	myfunction(PFUNC pfunc) :_pfunc(pfunc) {}
	R operator()(A1 arg1,A2 arg2)
	{
		return _pfunc(arg1,arg2);
	}
private:
	PFUNC _pfunc;
};
*/
//...表示可变参，A表示的是一组1类型，个数任意
template<typename R, typename... A>
class myfunction<R(A...)>
{
public:
	using PFUNC = R(*)(A...);
	myfunction(PFUNC pfunc) :_pfunc(pfunc) {}
	R operator()(A... arg)
	{
		return _pfunc(arg...);
	}
private:
	PFUNC _pfunc;
};
int main()
{
	myfunction<void(string)> func1(hello);
	func1("hello world");
	myfunction<int(int, int)> func2(sum);
	cout << func2(10, 20) << endl;
	return 0;
}

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


//C++11 bind 绑定器=>返回的结果是一个函数对象
void hello(string str) { cout << str << endl; }
int sum(int a, int b) { return a + b; }
class Test
{
public:
	int sum(int a, int b) { return a + b; }
};

int main()
{
	//bind是函数模板，可以自动推演模板类型参数
	bind(hello, "Hello bind!")();
	cout << bind(sum, 20, 30)() << endl;
	cout << bind(&Test::sum, Test(), 20, 30)() << endl;
	
	//function只接受一个类型,绑定器可以给相应的函数绑定固定的参数，绑定器只能使用在语句当中
	//参数占位符,绑定器出了语句，无法继续使用
	bind(hello, _1)("hello bind 2");
	cout << bind(sum, _1, _2)(20, 30) << endl;
	
	//此处把bind返回的绑定器binder就复用起来了
	function<void(string)> func1 = bind(hello, _1);
	func1("hello china!");
	func1("hello shan xi!");
	func1("hello da li!");

}

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

//线程类
class Thread
{
public:
	Thread(function<void(int)> func,int no):_func(func),_no(no){}
	thread start()
	{
		thread t(_func,_no);
		return t;
	}
private:
	function<void(int)> _func;
	int _no;
};
//线程池类
class ThreadPool
{
public:
	ThreadPool(){}
	~ThreadPool()
	{
		//释放thread对象占用的堆资源
		for (int i = 0; i < _pool.size(); i++)
		{
			delete _pool[i];
		}
	}
	//开启线程池
	void startPool(int size)
	{
		for (int i = 0; i < size; i++)
		{
			//不管是C++里面的thread还是Linux里面的pthread需要的线程函数都是一个C函数，是不能够使用成员方法的，因为它是C的函数类型，不可能把成员方法的函数指针给一个C的函数指针，接收不了。所以就需要绑定，把runInThread所依赖的参数全部绑定
			_pool.push_back(new Thread(bind(&ThreadPool::runInThread, this, _1),i));
		}
		for (int i = 0; i < size; i++)
		{
			_handler.push_back(_pool[i]->start());
		}
		for (thread& t : _handler)
		{
			t.join();
		}
	}
private:
	vector<Thread*> _pool;
	vector<thread> _handler;
	//把runInThread这个成员方法充当线程函数
	void runInThread(int id)
	{
		cout << "call runInThread! id:" << id << endl;
	}
};
int main()
{
	ThreadPool pool;
	pool.startPool(10);
	return 0;
}

#include<iostream>
using namespace std;
template<typename T=void>
class TestLambda01
{
public:
	void operator()()
	{
		cout << "hello world" << endl;
	}
};
template<typename T = int>
class TestLambda02
{
public:
	TestLambda02() {}
	int operator()(int a, int b)
	{
		return a + b;
	}
};
template<typename T = int>
class TestLambda03
{
public:
	TestLambda03(int a,int b):ma(a),mb(b){}
	void operator()()const
	{
		int tmp = ma;
		ma = mb;
		mb = tmp;
	}
private:
	mutable int ma;
	mutable int mb;
};
class TestLambda04
{
public:
	TestLambda04(int &a,int &b):ma(a),mb(b){}
	void operator()()const
	{
		int tmp = ma;
		ma = mb;
		mb = tmp;
	}
private:
	int& ma;
	int& mb;
};
int main()
{
	auto func1 = []()->void {cout << "hello world" << endl; };
	func1();

	auto func2 = [](int a, int b)->int {return a + b; };
	cout << func2(20, 30) << endl;

	int a = 10;
	int b = 20;
	//按值传递a,b值未被改变
	auto func3 = [a, b]()mutable
	{
		int tmp = a;
		a = b;
		b = tmp;
	};
	func3();
	cout << "a:" << a << " b:" << b << endl;
	
	//传引用值a,b值被改变
	auto func4 = [&]()
	{
		int tmp = a;
		a = b;
		b = tmp;
	};
	func4();
	cout << "a:" << a << " b:" << b << endl;

	cout << "--------------------" << endl;
	TestLambda01<> t1;
	t1();
	TestLambda02<> t2;
	cout << t2(20, 30) << endl;
	TestLambda03<> t3(a,b);
	t3();
	cout << "a:" << a << " b:" << b << endl;
	TestLambda04 t4(a,b);
	t4();
	cout << "a:" << a << " b:" << b << endl;
	
	return 0;
}

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

int main()
{
	vector<int> vec;
	for (int i = 0; i < 20; ++i)
	{
		vec.push_back(rand() % 100 + 1);
	}
	sort(vec.begin(), vec.end(),
		[](int a, int b)->bool
		{
			return a > b;
		});
	for (int val : vec)
	{
		cout << val << " ";
	}
	cout << endl;
	//65按序插入序列 要找一个小于65的数字
	auto it = find_if(vec.begin(), vec.end(),
		[](int a)->bool {return a < 65; });
	if (it != vec.end())
	{
		vec.insert(it, 65);
	}
	for (int val : vec)
	{
		cout << val << " ";
	}
	cout << endl;
	for_each(vec.begin(), vec.end(), [](int a)
	{
		if (a % 2 == 0)
			cout << a << " ";
	});
	cout << endl;
	return 0;
}

#include<iostream>
#include<vector>
#include<map>
#include<functional>
using namespace std;
int main()
{
	//auto只能出现在根据右边表达式推导左边的类型，只能使用在函数的局部作用域的范围之内
	//预先lambda表达式不知道需要先存储lambda表达式类型
	map<int, function<int(int, int)>> caculateMap;
	caculateMap[1] = [](int a, int b)->int {return a + b; };
	caculateMap[2] = [](int a, int b)->int {return a - b; };
	caculateMap[3] = [](int a, int b)->int {return a * b; };
	caculateMap[4] = [](int a, int b)->int {return a / b; };

	cout << "请选择";
	int choice;
	cin >> choice;
	cout << caculateMap[choice](10, 15) << endl;
	return 0;
}

#include<iostream>
#include<vector>
#include<functional>
using namespace std;
int main()
{
	unique_ptr<FILE, function<void(FILE*)>>
		ptr1(fopen("data.txt", "w"), [](FILE* pf) {fclose(pf); });
}

#include<iostream>
#include<vector>
#include<functional>
#include <queue>
using namespace std;

class Data
{
public:
	Data(int val1=10,int val2=10):ma(val1),mb(val2){}
	int ma;
	int mb;
};
int main()
{
	//优先级队列
	//priority_queue<Data> queue;
	using FUNC = function<bool(Data&, Data&)>;
	priority_queue<Data, vector<Data>, FUNC>
		maxHeap([](Data& d1, Data& d2)->bool
			{
				return d1.mb > d2.mb;
			});
	maxHeap.push(Data(10, 20));
	maxHeap.push(Data(15, 15));
	maxHeap.push(Data(20, 10));
}