1.函数对象使用

#include <iostream>
using namespace std;

//STL-函数对象（仿函数）

class MyAdd
{
public:
	int operator()(int v1, int v2)
	{
		return v1 + v2;
	}
};
//1、函数对象在使用时，可以像普通函数那用调用，可以有参数，可以有返回值
void test01()
{
	MyAdd myAdd;
	cout << myAdd(10, 10) << endl; 
}

// 2、函数对象超出普通函数的概念，函数对象可以有自己的状态
class MyPrint
{
public:
	MyPrint()
	{
		this->m_count = 0;
	}

	void operator()(string test)
	{
		cout << test << endl;
		this->m_count++;
	}

	int m_count; // 内部自己状态
};

void test02()
{
	MyPrint myPrint;
	myPrint("Hello World!");
	myPrint("Hello World!");
	myPrint("Hello World!");
	myPrint("Hello World!");

	cout << "MyPrint调用的次数： " << myPrint.m_count << endl;
}

void doPrint(MyPrint& mp, string test)
{
	mp(test);
}

// 3、函数对象可以作为参数传递
void test03()
{
	MyPrint myPrint;
	doPrint(myPrint, "Hello C++!");
}

int main()
{
	test01();
	cout << "------------------------" << endl << endl;
	test02();
	cout << "------------------------" << endl << endl;
	test03();

	//**************************************
	system("pause");
	return 0;
} 

2.谓词-一元谓词

#include <iostream>
using namespace std;

//STL-一元谓词
#include<vector>
#include<algorithm>

class GreaterFive
{
public:
	bool operator()(int val)
	{
		return val > 5;
	}
};

void test01()
{
	vector<int>v;
	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}

	//查找容器中 有没有大于5的数字
	//GreaterFive() 匿名函数对象
	vector<int>::iterator it = find_if(v.begin(), v.end(), GreaterFive());
	if (it == v.end())
	{
		cout << "未找到！" << endl;
	}
	else
	{
		cout << "找到了大于5的数字为：" << *it << endl;
	}
}

int main()
{
	test01();
	cout << "------------------------" << endl << endl;
	//test02();
	//cout << "------------------------" << endl << endl;
	//test03();

	//**************************************
	system("pause");
	return 0;
} 

3.二元谓词

#include <iostream>
using namespace std;

//STL-二元谓词

#include<vector>
#include<algorithm>

class MyCompare
{
public:
	bool operator()(int val1, int val2) //参数为两个 ， 二元谓词
	{
		return val1 > val2;  //降序
	}
};

void test01()
{
	vector<int>v;
	v.push_back(10);
	v.push_back(40);
	v.push_back(20);
	v.push_back(30);
	v.push_back(50);

	sort(v.begin(), v.end());
	for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;

	cout << "------------------------" << endl << endl;
	//使用函数对象 改变算法策略，变为排序规则 从大到小
	sort(v.begin(), v.end(), MyCompare());
	for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}

int main()
{
	test01();
	cout << "------------------------" << endl << endl;
	//test02();
	//cout << "------------------------" << endl << endl;
	//test03();

	//**************************************
	system("pause");
	return 0;
}