From 221ae46c2b9b48182542016505d6e03005c40512 Mon Sep 17 00:00:00 2001
From: cekc <31835620+cekc@users.noreply.github.com>
Date: Mon, 25 Feb 2019 18:35:53 +0300
Subject: [PATCH] add std::tuple_element and std::tuple_size specializations
 for index_value

To make index_value work with structured bindings
https://wandbox.org/permlink/gsveiKdAamnEbOKM
---
 include/boost/range/adaptor/indexed.hpp | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/boost/range/adaptor/indexed.hpp b/include/boost/range/adaptor/indexed.hpp
index a426bd6..8fd0289 100644
--- a/include/boost/range/adaptor/indexed.hpp
+++ b/include/boost/range/adaptor/indexed.hpp
@@ -367,4 +367,29 @@ index(
     } // namespace adaptors
 } // namespace boost
 
+#if !defined(BOOST_NO_CXX11_HDR_TUPLE)
+
+namespace std {
+
+#if defined(BOOST_CLANG)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wmismatched-tags"
+#endif
+
+template<size_t N, class T, class Indexable>
+struct tuple_element<N, boost::range::index_value<T, Indexable>>:
+    boost::tuples::element<N, boost::range::index_value<T, Indexable>> {};
+
+template<class T, class Indexable>
+struct tuple_size<boost::range::index_value<T, Indexable>>:
+    std::integral_constant<std::size_t, 2> {};
+
+#if defined(BOOST_CLANG)
+#pragma clang diagnostic pop
+#endif
+
+} // namespace std
+
+#endif // !defined(BOOST_NO_CXX11_HDR_TUPLE)
+
 #endif // include guard