#include <iostream> #include <sstream> #include <string> class CMyStream { public: typedef void (CMyStream::* EndlCallback)(); CMyStream& operator<<(EndlCallback pEndlCallback); template<typename T> CMyStream& operator<<(T Val) { //buffer the Val into stringstream std::stringstream ss; ss << Val; m_str += ss.str(); return *this; } void MyEndl(); //use std::cout to output private: std::string m_str; }; CMyStream::EndlCallback endl = &CMyStream::MyEndl; CMyStream& CMyStream::operator<<(CMyStream::EndlCallback pEndlCallback) { (this->*pEndlCallback)(); return *this; } void CMyStream::MyEndl(void) { std::cout << m_str << std::endl; m_str = ""; } int main() { CMyStream cout; cout << "hello" << endl; cout << "world";//call CMyStream& operator<<(T Val) cout <<endl; // endl = &CMyStream::MyEndl //=> so endl is a functor //=> call CMyStream& operator<<(EndlCallback pEndlCallback) override //=> in function: (this->*pEndlCallback)(); //=> at last call to: void CMyStream::MyEndl(void){...} return 0; }