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;
}