【C++】谓词

#include
using namespace std;
#include
#include
//仿函数 返回值类型是bool数据类型，称为谓词
//一元谓词

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

void test01()
{
	vectorv;
	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::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();
	system("pause");

	return 0;
}
//总结：参数只有一个的谓词称为一元谓词

#include
using namespace std;
#include
#include
//二元谓词

class MyCompare
{
public:
	bool operator()(int val1, int val2)
	{
		return val1 > val2;
	}


};

void test01()
{
	vectorv;
	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::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;

	//使用函数对象 改变算法策略，变为排序规则为从大到小
	sort(v.begin(), v.end(), MyCompare());

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


}

int main() {
	test01();
	system("pause");

	return 0;
}
//总结：参数只有两个的谓词，称为二元谓词