day18 谓词

谓词：返回bool类型的仿函数称为谓词

如果operator（）接收一个参数 就叫一元谓词

如果operator（）接收两个参数 就叫二元谓词

class compare 
{
public :
	bool operator()(int val) //一元谓词
	{
		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
	vector<int>::iterator it = find_if(v.begin(), v.end(), compare());//compare()匿名函数对象
	//find_if 返回的是迭代器
	if (it == v.end()) 
	{
		cout << "未找到" << endl;
	}
	else 
	{
		cout << "大于5的数字为" << *it << endl;
	}
}

class mycompare 
{
public:
	bool operator()(int v1 , int v2) 
	{
		return v1 > v2;
	}
};

//二元谓词
void test02()
{
	vector<int>v;
	v.push_back(4);
	v.push_back(12);
	v.push_back(45);
	v.push_back(66);
	v.push_back(1);
	/*sort(v.begin() , v.end());
	for (vector<int>::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() 
{
	test02();
	system("pause");
	return 0;
}