1[#nullary_metafunction] 2[section Nullary template metafunction] 3 4A ['nullary template metafuncion] is a [link metafunction template metafunction] 5taking 0 arguments. It is a type with a nested type called `type`, which is the 6return value of the nullary metafunction. For example: 7 8 struct always13 9 { 10 using type = std::integral_constant<int, 13>; 11 }; 12 13This metafunction is called `always13`. It is a nullary metafunction, because it 14takes no arguments. It always returns `std::integral_constant<int, 13>`. 15 16To call this metafunction, one has to access its `::type`. For example: 17 18 always13::type 19 20The above example calls the metafunction to get 21`std::integral_constant<int, 13>`. 22 23[endsect] 24 25