C++STL 预定义函数对象和函数适配器

void main()
{
	plus<int> intAdd;
	int x = 10;
	int y = 20;
	int z = intAdd(x, y); //等价于 x + y 
	cout << z << endl;

	plus<string> stringAdd;
	string myc = stringAdd("aaa", "bbb");
	cout << myc << endl;

	vector<string> v1;
	v1.push_back("bbb");
	v1.push_back("aaa");
	v1.push_back("ccc");
	v1.push_back("zzzz");
}

void main()
{
	vector<string> v1;
	v1.push_back("bbb");
	v1.push_back("aaa");
	v1.push_back("ccc");
	v1.push_back("zzzz");
	v1.push_back("ccc");
	string s1 = "ccc";
	//int num = count_if(v1.begin(),v1.end(), equal_to<string>(),s1);
	int num = count_if(v1.begin(),v1.end(),bind2nd(equal_to<string>(), s1));//bind2nd函数适配器
	cout << num << endl;
} 

class IsGreat
{
public:
	IsGreat(int i)
	{
		m_num = i;
	}
	bool operator()(int &num)
	{
		if (num > m_num)
		{
			return true;
		}
		return false;
	}
protected:
private:
	int m_num;
};

void main()
{
	vector<int>  v1;
	for (int i=0; i<5; i++)
	{
		v1.push_back(i+1);
	}

	for (vector<int>::iterator it = v1.begin(); it!=v1.end(); it ++)
	{
		cout << *it << " " ;
	}

	int num1 = count(v1.begin(), v1.end(), 3);
	cout << "num1:" << num1 << endl;

	//通过谓词求大于2的个数
	int num2 = count_if(v1.begin(), v1.end(), IsGreat(2)); 
	cout << "num2:" << num2 << endl;

	//通过预定义函数对象求大于2的个数   greater<int>() 有2个参数 
	//												param > 2
	int num3 = count_if(v1.begin(), v1.end(), bind2nd(greater<int>(), 2 ) );
	cout << "num3:" << num3 << endl;

	//取模 能被2整除的数 求奇数
	int num4 = count_if(v1.begin(), v1.end(), bind2nd(modulus <int>(), 2 ) ); 
	cout << "奇数num4:" << num4 << endl;

	int num5 = count_if(v1.begin(), v1.end(), not1( bind2nd(modulus <int>(), 2 ) ) ); 
	cout << "偶数num5:" << num5 << endl;
	return ;
}