1 files changed, 34 insertions, 0 deletions
diff --git a/boost/histogram/detail/tuple_slice.hpp b/boost/histogram/detail/tuple_slice.hpp
new file mode 100644
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+++ b/boost/histogram/detail/tuple_slice.hpp
@@ -0,0 +1,34 @@
+// Copyright 2015-2019 Hans Dembinski
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_HISTOGRAM_DETAIL_TUPLE_SLICE_HPP
+#define BOOST_HISTOGRAM_DETAIL_TUPLE_SLICE_HPP
+
+#include <boost/mp11/integer_sequence.hpp>
+#include <tuple>
+#include <type_traits>
+
+namespace boost {
+namespace histogram {
+namespace detail {
+
+template <std::size_t I, class T, std::size_t... K>
+decltype(auto) tuple_slice_impl(T&& t, mp11::index_sequence<K...>) {
+  return std::forward_as_tuple(std::get<(I + K)>(std::forward<T>(t))...);
+}
+
+template <std::size_t I, std::size_t N, class Tuple>
+decltype(auto) tuple_slice(Tuple&& t) {
+  constexpr auto S = std::tuple_size<std::decay_t<Tuple>>::value;
+  static_assert(I + N <= S, "I, N must be a valid subset");
+  return tuple_slice_impl<I>(std::forward<Tuple>(t), mp11::make_index_sequence<N>{});
+}
+
+} // namespace detail
+} // namespace histogram
+} // namespace boost
+
+#endif