tuple_visitor.hh

Go to the documentation of this file.

/*
    @@@@@@@@  @@           @@@@@@   @@@@@@@@ @@
   /@@/////  /@@          @@////@@ @@////// /@@
   /@@       /@@  @@@@@  @@    // /@@       /@@
   /@@@@@@@  /@@ @@///@@/@@       /@@@@@@@@@/@@
   /@@////   /@@/@@@@@@@/@@       ////////@@/@@
   /@@       /@@/@@//// //@@    @@       /@@/@@
   /@@       @@@//@@@@@@ //@@@@@@  @@@@@@@@ /@@
   //       ///  //////   //////  ////////  //

   Copyright (c) 2016, Triad National Security, LLC
   All rights reserved.
                                                                              */
#pragma once

#include <tuple>

namespace flecsi {
namespace util {

template<typename _Tuple, typename _Fn, size_t... _Idx>
void
tuple_visitor_impl(_Tuple && t, _Fn && f, std::index_sequence<_Idx...>) {
  /*
    This creates an initializer list so that the index sequence is
    expanded properly. The (f(x), 0) uses the comma operator so
    that f is evaluated, but the resulting value is discarded. The value
    of the entire expression is 0.

    Attribution: Andy Prowl on stackoverflow.
   */
  auto _l = {(f(_Idx, std::get<_Idx>(t)), 0)...};
}

template<typename _Tuple, typename _Fn>
void
tuple_visitor(_Tuple && t, _Fn && f) {
  using _Indices =
    std::make_index_sequence<std::tuple_size_v<std::decay_t<_Tuple>>>;

  tuple_visitor_impl(std::forward<_Tuple>(t), std::forward<_Fn>(f), _Indices{});
}

template<typename _Tuple, typename _Fn>
void
tuple_visitor(_Fn && f) {
  static_assert(std::is_default_constructible<_Tuple>::value,
    "tuple_vist tuple type is not default constructible");

  using _Indices =
    std::make_index_sequence<std::tuple_size_v<std::decay_t<_Tuple>>>;

  tuple_visitor_impl(
    std::forward<_Tuple>({}), std::forward<_Fn>(f), _Indices{});
}

} // namespace util
} // namespace flecsi