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
#ifndef DUO_HPP
#define DUO_HPP
template <typename T1, typename T2>
class Duo {
public:
typedef T1 Type1; // type of first field
typedef T2 Type2; // type of second field
enum { N = 2 }; // 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;
}
};
// comparison operators (allow mixed types):
template <typename T1, typename T2,
typename U1, typename U2>
inline
bool operator == (Duo<T1,T2> const& d1, Duo<U1,U2> const& d2)
{
return d1.v1()==d2.v1() && d1.v2()==d2.v2();
}
template <typename T1, typename T2,
typename U1, typename U2>
inline
bool operator != (Duo<T1,T2> const& d1, Duo<U1,U2> const& d2)
{
return !(d1==d2);
}
// convenience function for creation and initialization
template <typename T1, typename T2>
inline
Duo<T1,T2> make_duo (T1 const & a, T2 const & b)
{
return Duo<T1,T2>(a,b);
}
#endif // DUO_HPP