frnd2tmp.cpp
来源: C++ 中的代码重用
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// frnd2tmp.cpp -- template class with non-template friends
#include <iostream>
using std::cout;
using std::endl;
template <typename T>
class HasFriend
{
private:
T item;
static int ct;
public:
HasFriend(const T & i) : item(i) {ct++;}
~HasFriend() {ct--; }
friend void counts();
friend void reports(HasFriend<T> &); // template parameter
};
// each specialization has its own static data member
template <typename T>
int HasFriend<T>::ct = 0;
// non-template friend to all HasFriend<T> classes
void counts()
{
cout << "int count: " << HasFriend<int>::ct << "; ";
cout << "double count: " << HasFriend<double>::ct << endl;
}
// non-template friend to the HasFriend<int> class
void reports(HasFriend<int> & hf)
{
cout <<"HasFriend<int>: " << hf.item << endl;
}
// non-template friend to the HasFriend<double> class
void reports(HasFriend<double> & hf)
{
cout <<"HasFriend<double>: " << hf.item << endl;
}
int main()
{
cout << "No objects declared: ";
counts();
HasFriend<int> hfi1(10);
cout << "After hfi1 declared: ";
counts();
HasFriend<int> hfi2(20);
cout << "After hfi2 declared: ";
counts();
HasFriend<double> hfdb(10.5);
cout << "After hfdb declared: ";
counts();
reports(hfi1);
reports(hfi2);
reports(hfdb);
// std::cin.get();
return 0;
}
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