What's the point of unnamed non-type template parameters?

Question

According to the reference, the name of a non-type template parameter is optional, even when assigning a default value (see (1) and (2)). Therefore these template structs ar

Answer 1

First, we can split declaration from definition. So name in declaration is not really helpful. and name might be used in definition

template  struct Foo;
template  struct Bar;

template  struct Foo {/*..*/};
template  struct Bar {/*..*/};

Specialization is a special case of definition.

Then name can be unused, so we might omit it:

template 
using always_t = T;

template 
struct MyArray, T>
{
    MyArray(always_t... v) : /*..*/
};

or used for SFINAE

template 
struct some_sized_type;