code for template

// A example for template

// From <<An introduction to object-oriented programming>> P273



#include <iostream>

#include <string>

#include <list>

using namespace std;



// class Apple

class Apple {

public:

    Apple() : variety("generic") {}

    Apple(string & v) : variety(v) {}

    Apple(const Apple & a) : variety(a.variety) {}



    ostream & print_on(ostream & out) {

        return out << "Apple: " << variety;

    }

private:

    string variety;

};



// class Orange

class Orange {

public:

    Orange() {}



    ostream & write_to(ostream & out) {

        return out << "Orange";

    }

};





// Common function for output stream

void print(Apple & a, ostream & out) {

    a.print_on(out);

}



void print(Orange & r, ostream & out) {

    r.write_to(out);

}





// Class Fruit

class Fruit {

public:

    virtual void print(ostream & out) = 0;

};



template <class T>

class FruitAdapter : public Fruit {

public:

    FruitAdapter(T & t) : the_fruit(t) {}



    T & value() {

        return the_fruit;

    }



    virtual void print(ostream & out) {

        ::print(the_fruit, out);

    }

public:

    T & the_fruit;

};



template <class T>

Fruit * new_Fruit(T & t) {

    return new FruitAdapter<T>(t);

}



int main(int argc, char * argv[])

{

    Apple apple;

    Orange orange;



    list<Fruit *> fruit_list;



    fruit_list.insert(fruit_list.end(), new_Fruit(apple));

    fruit_list.insert(fruit_list.end(), new_Fruit(orange));



    list<Fruit *>::iterator start = fruit_list.begin();

    list<Fruit *>::iterator stop = fruit_list.end();



    for (; start != stop; start++) {

        (*start)->print(cout);

    }



    return 0;

}