class Add
{
 public:
 double operator()(double x,double y)
 {
   return x+y;
 }
};

Add plus;   //plus就是一个函数对象
cout<<plus(1.2,3.4)<<endl;//通过函数对象调用重载函数
cout<<Add()(1.2,3.4)<<endl; //Add()会创建一个临时对象

#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
using namespace std;
/*
class absInt {

};
*/ //class和struct都是定义类，struct成员默认属性为public

void print(double i)
{
    cout << i << " ";
}

void myforeach(vector<double>::iterator & t1, vector<double>::iterator & t2, void(*fun)(double i))//可以通过函数指针将一个函数作为另一个函数的参数
{
    while (t1 != t2)
    {
        fun(*t1);
        ++t1;
    }
}

struct absInt {
    //重载操作符()
    int operator()(int val)
    {
        return val < 0 ? -val : val;
    }
};
template <typename elementType>
void FuncDisplayElement(const elementType & element)
{
    cout << element << " " ;
}

template <typename elementType>
struct DisplayElement {
    //存储状态
    int m_nCount;
    DisplayElement()
    {
        m_nCount = 0;
    }
    void operator()(const elementType & element)
    {
        ++m_nCount;
        cout << element << " ";
    }
};
int main()
{
    absInt absObj;//函数对象
    int i = -2;
    unsigned int ui = absObj(i);//通过函数对象调用函数
    cout << ui << endl;

    vector<int> a;
    for (int i = 0; i < 10; i++)
    {
        a.push_back(i);
    }

    DisplayElement<int> mResult;
    mResult = for_each(a.begin(), a.end(), mResult);//把函数对象作为参数传递给另一个函数
    cout << endl;
    cout << "数量" << mResult.m_nCount << endl;

    list<char> b;
    for (char c = 'a'; c < 'k'; ++c)
    {
        b.push_back(c);
    }

    for_each(b.begin(), b.end(), DisplayElement<char>());//DisplayElement<char>()会创建一个临时对象
    cout << endl;

    vector<double> vec = { 76,92,86,74,95 };
    cout << "vec里的类容为:" << endl;
    for_each(vec.begin(), vec.end(), print);
    cout << "vec里的内容为" << endl;
    myforeach(vec.begin(), vec.end(), print);

    getchar();
    return 0;
}

#include <iostream>
#include <string>
using namespace std;
struct student {
    string sno;
    student()
    {
        cout << "调用构造函数son为:" << sno << "#"<<endl;
    }
    student(string sno)
    {
        this->sno = sno;
        cout << "调用构造函数sno为:" << this->sno << "#" << endl;
    }

    void operator()(string sno)
    {
        this->sno = sno;
        cout << "调用函数对象sno为:" << this->sno << "#" << endl;
    }
};
int main()
{
    student s("2014");//输出"调用构造函数sno为：2014#"
    student  s2;     //输出"调用构造函数sno为：#"
    s("2014");      //输出"调用函数对象sno为：2014#"
    getchar();
    return 0;
}