box2.cpp

很经典的书籍

//: C05:Box2.cpp
// Defines non-template operators
#include <iostream>
using namespace std;

template<class T>
class Box {
  T t;
public:
  Box(const T& theT) : t(theT) {}
  friend Box operator+(const Box<T>& b1,
                         const Box<T>& b2) {
    return Box<T>(b1.t + b2.t);
  }
  friend ostream& operator<<(ostream& os,
                               const Box<T>& b) {
    return os << '[' << b.t << ']';
  }
};

int main() {
  Box<int> b1(1), b2(2);
  cout << b1 + b2 << endl;  // [3]
  cout << b1 + 2 << endl;   // [3]
} ///:~