STL学习笔记（15）函数对象适配器

class MyPrint : public binary_function<int, int, void>
{
public:
    void operator()(int v1, int v2) const { cout << "v1 = : " << v1 << " v2 = :" << v2 << " v1+v2 = :" << (v1 + v2) << endl; }
};

//1、函数适配器
void test01()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    cout << "请输入起始值：" << endl;
    int x;
    cin >> x;
    for_each(v.begin(), v.end(), bind1st(MyPrint(), x));
    //for_each(v.begin(), v.end(), bind2nd( MyPrint(),x ));
}

//总结： bind1st 和 bind2nd 区别?
//bind1st ： 将参数绑定为函数对象的第一个参数
//bind2nd ： 将参数绑定为函数对象的第二个参数
//bind1st bind2nd 将二元函数对象转为一元函数对象

class GreaterThenFive : public unary_function<int, bool>
{
public:
    bool operator()(int v) const { return v > 5; }
};

//2、取反适配器
void test02()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }

    // vector<int>::iterator it = find_if(v.begin(), v.end(), GreaterThenFive()); //返回 第一个大于 5 的迭代器
    // vector<int>::iterator it = find_if(v.begin(), v.end(), not1(GreaterThenFive())); //返回第一个小于 5 迭代器
    //自定义输入
    vector<int>::iterator it = find_if(v.begin(), v.end(), not1(bind2nd(greater<int>(), 5)));
    if (it == v.end())
    {
        cout << "没找到" << endl;
    }
    else
    {
        cout << "找到" << *it << endl;
    }

    //排序 二元函数对象
    sort(v.begin(), v.end(), not2(less<int>()));
    for_each(v.begin(), v.end(), [](int val)
             { cout << val << " "; });
}
//not1 对一元函数对象取反
//not2 对二元函数对象取反

void MyPrint03(int v, int v2)
{
    cout << v + v2 << " ";
}

//3、函数指针适配器 ptr_fun
void test03()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);

    } // ptr_fun( )把一个普通的函数指针适配成函数对象
    for_each(v.begin(), v.end(), bind2nd(ptr_fun(MyPrint03), 100));
}

//4、成员函数适配器
class Person
{
public:
    Person(string name, int age)
    {
        m_Name = name;
        m_Age = age;
    }
    //打印函数
    void ShowPerson()
    {
        cout << "成员函数:"
             << "Name:" << m_Name << " Age:" << m_Age << endl;
    }
    void Plus100() { m_Age += 100; }

public:
    string m_Name;
    int m_Age;
};

void MyPrint04(Person &p)
{
    cout << "姓名：" << p.m_Name << " 年龄：" << p.m_Age << endl;
};

void test04()
{
    vector<Person> v;
    Person p1("aaa", 10);
    Person p2("bbb", 20);
    Person p3("ccc", 30);
    Person p4("ddd", 40);
    v.push_back(p1);
    v.push_back(p2);
    v.push_back(p3);
    v.push_back(p4);
    //for_each(v.begin(), v.end(), MyPrint04); //利用 mem_fun_ref 将 Person 内部成员函数适配
    for_each(v.begin(), v.end(), mem_fun_ref(&Person::ShowPerson));
    // for_each(v.begin(), v.end(), mem_fun_ref(&Person::Plus100));
    // for_each(v.begin(), v.end(), mem_fun_ref(&Person::ShowPerson));
}

void test05()
{
    vector<Person *> v1; //创建数据
    Person p1("aaa", 10);
    Person p2("bbb", 20);
    Person p3("ccc", 30);
    Person p4("ddd", 40);
    v1.push_back(&p1);
    v1.push_back(&p2);
    v1.push_back(&p3);
    v1.push_back(&p4);
    for_each(v1.begin(), v1.end(), mem_fun(&Person::ShowPerson));
}
//如果容器存放的是对象指针， 那么用 mem_fun
//如果容器中存放的是对象实体，那么用 mem_fun_ref