example2.cpp

struct Dog {};

struct Husky : public Dog {};
struct Poodle :public Dog {};

template<class T>
struct is_husky {
	static constexpr bool result = false;
};
template<>
struct is_husky<Husky> {
	static constexpr bool result = true;
};

template<typename T>
concept bool ExceptHusky = !is_husky<T>::result; // If T is husky, this concept returns false

template<ExceptHusky T>
void DogCanBeSmartExceptHusky(const T&& dog) {};

/*
template<class T> requires ExceptHusky<T> 
void DogCanBeSmartExceptHusky(const T&& dog) {}; 
also works. This is for multiple require expressions, they can use ||, &, ! such operators to join
*/

int main()
{
	DogCanBeSmartExceptHusky(Poodle{});
	DogCanBeSmartExceptHusky(Husky{}); 
	// Error message here: 
	// constraints not satisfied
	//'!(is_husky<Husky>::result)' evaluated to false
}