20 General utilities library [utilities]

20.5 Compile-time integer sequences [intseq]

20.5.1 In general [intseq.general]

The library provides a class template that can represent an integer sequence. When used as an argument to a function template the parameter pack defining the sequence can be deduced and used in a pack expansion.


template<class F, class Tuple, std::size_t... I>
  decltype(auto) apply_impl(F&& f, Tuple&& t, index_sequence<I...>) {
    return std::forward<F>(f)(std::get<I>(std::forward<Tuple>(t))...);

template<class F, class Tuple>
  decltype(auto) apply(F&& f, Tuple&& t) {
    using Indices = make_index_sequence<std::tuple_size<std::decay_t<Tuple>>::value>;
    return apply_impl(std::forward<F>(f), std::forward<Tuple>(t), Indices());

 — end example ] [ Note: The index_sequence alias template is provided for the common case of an integer sequence of type size_t.  — end note ]