函数对象
#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<functional>
#include<vector>
#include<algorithm>
using namespace std;
bool func(int val1,int val2)
{return val1 > val2;
}
void test()
{vector<int>v;v.push_back(2);v.push_back(7);v.push_back(4);//sort(v.begin(), v.end(),func);//降序sort(v.begin(), v.end(), greater<int>());for_each(v.begin(), v.end(), [](int val) {cout << val << " "; });//[](int val) {cout << val << " "; }[]是匿名函数
}
//函数对象与普通函数的区别
//1：函数对象能有自己的状态
//2：普通函数没有类型，但函数对象有
//3：函数对象比普通函数更有效率，（成员函数自动申请为内联函数）
void test01()
{plus<int>myplus;cout << myplus(3, 5) << endl;
}
int main()
{test01();system("pause");return 0;
}适配器
#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<functional>
#include<vector>
#include<algorithm>
using namespace std;
void print(int val)
{cout << val << " ";
}
struct myfunc
{bool operator()(int val){cout << val << " "<<endl;return true;}
};
//struct myfunc2
//{
// bool operator()(int val)
// {
// cout << val + 10 << " ";
// return true;
// }
//};
//第一步：继承binary_function<参数一，参数二，返回类型>
struct myfunc2 :public binary_function<int, int, void>
{void operator()(int val1, int val2)const{cout << val1 + val2 << " ";//第三步实现函数体}
};
void test()
{vector<int>v;v.push_back(2);v.push_back(34);v.push_back(122);//for_each(v.begin(), v.end(), print);for_each(v.begin(), v.end(), myfunc());//返回时每个都加十for_each(v.begin(), v.end(), bind2nd(myfunc2(),10));//第四步：用bind2nd绑定函数对象
}
//bind1st把10绑定给第一个参数，bind2nd把10绑定给第二个参数
//函数对象适配器not1 not2取反
//1：not1和not2区别：not1针对一元函数对象，not2针对二元函数对象
//第一步：继承
struct mynotfunc:public unary_function<int,bool>
{bool operator()(int val)const//第二步：变常函数{return val >= 20;}
};
int myfind(int val)
{return val > 20;
}
void test02()
{vector<int>v;v.push_back(2);v.push_back(34);v.push_back(122);vector<int>::iterator it=find_if(v.begin(), v.end(),not1( mynotfunc()));//第三步：适配//vector<int>::iterator it = find_if(v.begin(), v.end(), myfind);if (it == v.end()){cout << " 查找失败" << endl;}else{cout << " 查找成功" << *it << endl;//结果：打印出2}
}
//not2的使用
struct myprint
{bool operator()(int val1){cout << val1 << " ";return true;}};
struct mysort
{bool operator()(int val1, int val2){return val1 > val2;}
};
void test03()
{vector<int>v;v.push_back(2);v.push_back(34);v.push_back(122);//sort(v.begin(), v.end(),mysort());//debug下会报错sort(v.begin(), v.end(), not2(less<int>()));//for_each(v.begin(), v.end(), myprint());for_each(v.begin(), v.end(), [](int val) {cout << val << " "; });
}
//普通函数进行适配
//第一步：把一个参数变两个参数
void myprint1(int val,int val2)
{cout << val+val2 << " ";
}
void test04()
{vector<int>v;v.push_back(2);v.push_back(34);v.push_back(122);//第二步：把普通函数变函数对象ptr_funfor_each(v.begin(), v.end(), bind2nd(ptr_fun(myprint1),100));
}
//成员函数适配
class maker
{
public:maker(string name, int age){this->name = name;this->age = age;}void myprint2(){cout << "name:" << name << " " << "age:" <<age << endl;}
public:string name;int age;
};
//void myprint2(maker& m)
//{
// cout << "name:" << m.name << " " << "age:" << m.age << endl;
//}void test05()
{vector<maker>v;v.push_back(maker("aaa", 10));v.push_back((maker("huihui", 18)));v.push_back(maker("hhh", 20));//for_each(v.begin(), v.end(), myprint2);//当容器存储的是对象，用mem_fun_ref来适配它的成员函数for_each(v.begin(), v.end(),mem_fun_ref( & maker::myprint2));vector<maker*>v2;v2.push_back(new maker("aaa", 10));v2.push_back((new maker("huihui", 18)));v2.push_back(new maker("hhh", 20));//当容器存储的是对象指针，用mem_fun来适配它的成员函数for_each(v2.begin(), v2.end(), mem_fun(&maker::myprint2));}
int main()
{test05();system("pause");return 0;
}
)
