详解C++11中绑定器bind的原理与使用

class Print {
public:
    void operator()(string &s) { cout << s << endl; }
};

int main() {
    string s = "hello world!";
    Print print; //定义了一个函数对象print
    print(s);
    return 0;
}

sort(vec.begin(), vec.end(), greater<int>()); //从大到小对vector进行排序
find\_if(vec.begin(), vec.end(), bind1st(greater<int>(), 70));
find\_if(vec.begin(), vec.end(), bind2nd(less<int>(), 70));

#include <iOStream>
#include <vector>
#include <functional>
#include <alGorithm>
#include <ctime>
using namespace std;


template<typename Container>

void printerContainer(Container  & _container) {

	typename Container::iterator it_begin = _container.begin();
	typename Container::iterator it_end   = _container.end();
	while (it_begin != it_end) {
		cout << *it_begin <<" " ;
		++it_begin;
	}

}

int main() {

	vector < int>  vec;
	srand(time(nullptr));
	for (int i = 0; i < 20; i++) {
		vec.push_back((rand() % 100 + 1));		
	}

	printerContainer<vector < int>>(vec);

	vector< int>::iterator it_begin= vec.begin();
	vector< int>::iterator it_end  = vec.end();

	sort(it_begin, it_end);//默认小到大排序
	cout << endl;
	printerContainer<vector < int>>(vec);

	cout << endl;
	//greater二元函数对象
	sort(it_begin, it_end,greater<int>());//大到小排序
	printerContainer<vector < int>>(vec);

	cout << endl;

	//将70按顺序插入容器中,找到第一个小于70的元素
	//库里提供的less,greater都是二元的函数对象
	//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) 	
	//greater
	//constexpr bool operator()(const _Ty& _Left, const _Ty& _Right) const
	//{	// apply operator> to operands
	//	return (_Left > _Right);
	//}
 
	//bind2nd: + less bool operator()(const _Ty& _Left, 70) 

	vector<int>::iterator  it_findValue=find_if(it_begin, it_end, bind1st<greater<int>, int>(greater<int>(), 70));
	if (it_findValue != it_end) {
		vec.insert(it_findValue, 70);
	}
	printerContainer<vector < int>>(vec);

	cout << endl;

	system("pause");

	return 0;
}

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <functional>
#include <ctime>
using namespace std;

template<typename Container>
void printContainter(Container _container) {
	typename Container::iterator  it_begin = _container.begin();
	typename Container::iterator  it_end = _container.end();

	for (; it_begin != it_end; ++it_begin) {
		cout << *it_begin << " ";
	}
	cout << endl;
}


//将二元函数对象分装,返回一元函数对象
template<typename Pr, typename T>
class MyBindList2 {

public:
	MyBindList2<Pr,T>(Pr _pr, T _val):_mPr(_pr),_mVal(_val) {}
	bool operator()(T _paremeter) {
		return _mPr(_mVal, _paremeter);
	}
private:
	Pr _mPr;
	T  _mVal;
};

//Iterator 迭代器
//Pr 一元函数对象
template<typename Iterator , typename Pr>
Iterator my_find_if_v2(Iterator it_begin, Iterator it_end, Pr _pre) {
	for (; it_begin != it_end; ++it_begin) {
		if (_pre(*it_begin)) { return it_begin; }
	}
	return it_end;
}



int main() {

	vector<int> v1;
	srand(time(nullptr));
	for (int i = 0; i < 10; i++) {
		v1.push_back((rand() % 100 + 1));
	}

	printContainter<vector<int>>(v1);

	//升序
	sort(v1.begin(), v1.end(), less<int>());

	//sort(v1.begin(), v1.end(), greater<int>()); 降序

	printContainter<vector<int>>(v1);



	
	//  方法 一
    #if 0

	vector<int>::iterator it_begin = v1.begin();
	vector<int>::iterator it_end   = v1.end();

	for (; it_begin!=it_end; ++it_begin) {
		if (*it_begin > 40) {  break ;}
	}
	if (it_begin != it_end) {
		v1.insert(it_begin,40);
	}
	printContainter<vector<int>>(v1);
   #endif 


 	//  方法 二 自己实现Bind1st
    #if 0 自己实现Bind1st
	vector<int>::iterator it_find = my_find_if_v2<vector<int>::iterator, MyBindList2<less<int>, int>>(v1.begin(), v1.end(), MyBindList2<less<int>, int>(less<int>(), 40));

	v1.insert(it_find, 40);

	printContainter<vector<int>>(v1);

    #endif 

	//  方法 三  调用库的Bind1st

    vector<int>::iterator find_it2=find_if<vector<int>::iterator, binder1st<less<int>>>(v1.begin(), v1.end(), bind1st<less<int>, int>(less<int>(), 40));
	v1.insert(find_it2, 40);

	printContainter<vector<int>>(v1);

	system("pause");
	return 0;



}