The following code example is taken from the book
C++ Templates - The Complete Guide
by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
© Copyright David Vandevoorde and Nicolai M. Josuttis 2002
template <typename A, typename B, typename C>
class Duo<A, Duo<B,C> > {
public:
typedef A T1; // type of first field
typedef Duo<B,C> T2; // type of second field
enum { N = Duo<B,C>::N + 1 }; // number of fields
private:
T1 value1; // value of first field
T2 value2; // value of second field
public:
// constructors
Duo() : value1(), value2() {
}
Duo (T1 const & a, T2 const & b)
: value1(a), value2(b) {
}
// for implicit type conversion during construction
template <typename U1, typename U2>
Duo (Duo<U1,U2> const & d)
: value1(d.v1()), value2(d.v2()) {
}
// for implicit type conversion during assignments
template <typename U1, typename U2>
Duo<T1, T2>& operator = (Duo<U1,U2> const & d) {
value1 = d.value1;
value2 = d.value2;
return *this;
}
// field access
T1& v1() {
return value1;
}
T1 const& v1() const {
return value1;
}
T2& v2() {
return value2;
}
T2 const& v2() const {
return value2;
}
};