Trace Specialized Counters and Printing Overloads

1#include <iostream>
2#include <utility>
3 
4template <typename T>
5class Foo {
6    T m_value;
7public:
8    static int counter;
9    Foo(T value) : m_value(value) {}
10    T value() const { return m_value; }
11};
12 
13template <typename T>
14int Foo<T>::counter = 55;
15 
16template <>
17int Foo<double>::counter = 20;
18 
19template <typename T>
20std::ostream& operator<<(std::ostream& os, Foo<T>& foo) {
21    Foo<T>::counter += 1;
22    os << "lvalue " << foo.value() << " " << Foo<T>::counter;
23    return os;
24}
25 
26template <typename T>
27std::ostream& operator<<(std::ostream& os, Foo<T>&& foo) {
28    Foo<T>::counter += 2;
29    os << "rvalue " << foo.value() << " " << Foo<T>::counter;
30    return os;
31}
32 
33int main() {
34    Foo<int> a(1);
35    Foo<int> b(2);
36    Foo<double> d(2.5);
37    std::cout << a << "\n";
38    std::cout << b << "\n";
39    std::cout << Foo<int>(3) << "\n";
40    std::cout << d << "\n";
41    std::cout << std::move(d) << "\n";
42    std::cout << a << "\n";
43    return 0;
44}