Is a parameter pack a template parameter?

Question

cppreference writes that a template parameter pack is a template parameter:

https://en.cppreference.com/w/cpp/language/parameter_pack

Is it true? For example, is it correct to write something like this:

template<typename... Ts>
class MyClass {
    std::unique_ptr<Ts...> m_data;
};

Answer 1

Yes, a parameter pack is a valid template parameter, to use in a declaration. But when a template is instantiated, it is replaced with a list of actually supplied template arguments, see https://en.cppreference.com/w/cpp/language/template_parameters

E.g. in your example MyClass<int> will contain std::unique_ptr<int>, MyClass<int, MyDeleter> will contain std::unique_ptr<int, MyDeleter> and MyClass<int, MyDeleter, Foo> will cause a compiler error "wrong number of template arguments", because std::unique_ptr may have at most two of them.