仿函数：重载operator（）的类

第一个仿函数的demo：

仿函数，就是实现了operator（）重载的类。

“Generically, function objects are instances of a class with member function operator() defined. This member function allows the object to be used with the same syntax as a regular function call, and therefore it can be used in templates instead of a pointer to a function.” —— www.cplusplus.com

#include<algorithm>
#include<iostream>
#include<vector>
using namespace std;
class CSum //仿函数类CSum
{
private:
    int sum;
public:
    CSum(){sum=0;}
    void operator()(int n){sum += n;}//重载了operator（）运算符

    int getSum(){return sum;}
};

int main(int argc,char**argv)
{
    vector<int> v;
    for(int i=0;i<100;++i)
        v.push_back(i);
    //我怀疑CSum（）等同于两步，1是调用构造函数创建CSum对象并初始化sum，2是调用了100次重载函数operator（） 

    CSum obj = for_each(v.begin(),v.end(),CSum());
    cout<<obj.getSum()<<endl;
    cin.get();
    return 0;
}