The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,
Addison-Wesley, 2017
© Copyright David Vandevoorde, Nicolai M. Josuttis, Douglas Gregor 2017
#include <exception>
#include "isequalitycomparable.hpp"
template<typename T,
bool EqComparable = IsEqualityComparable<T>::value>
struct TryEquals
{
static bool equals(T const& x1, T const& x2) {
return x1 == x2;
}
};
class NotEqualityComparable : public std::exception
{
};
template<typename T>
struct TryEquals<T, false>
{
static bool equals(T const& x1, T const& x2) {
throw NotEqualityComparable();
}
};