From c61a4f691ed6ebee9f2dae7d001ac4f652a518c2 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Sun, 27 Nov 2022 21:20:19 +0200
Subject: [PATCH] Add boost::container_hash::is_tuple_like. Refs #30.

---
 .../boost/container_hash/is_tuple_like.hpp    | 41 +++++++++
 test/Jamfile.v2                               |  2 +
 test/is_tuple_like_test.cpp                   | 86 +++++++++++++++++++
 3 files changed, 129 insertions(+)
 create mode 100644 include/boost/container_hash/is_tuple_like.hpp
 create mode 100644 test/is_tuple_like_test.cpp

diff --git a/include/boost/container_hash/is_tuple_like.hpp b/include/boost/container_hash/is_tuple_like.hpp
new file mode 100644
index 0000000..5368283
--- /dev/null
+++ b/include/boost/container_hash/is_tuple_like.hpp
@@ -0,0 +1,41 @@
+#ifndef BOOST_HASH_IS_TUPLE_LIKE_HPP_INCLUDED
+#define BOOST_HASH_IS_TUPLE_LIKE_HPP_INCLUDED
+
+// Copyright 2017, 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/type_traits/integral_constant.hpp>
+#include <boost/config.hpp>
+#include <utility>
+
+namespace boost
+{
+namespace hash_detail
+{
+
+template<class T, class E = true_type> struct is_tuple_like_: false_type
+{
+};
+
+#if !defined(BOOST_NO_CXX11_HDR_TUPLE)
+
+template<class T> struct is_tuple_like_<T, integral_constant<bool, std::tuple_size<T>::value == std::tuple_size<T>::value> >: true_type
+{
+};
+
+#endif
+
+} // namespace hash_detail
+
+namespace container_hash
+{
+
+template<class T> struct is_tuple_like: hash_detail::is_tuple_like_<T>
+{
+};
+
+} // namespace container_hash
+} // namespace boost
+
+#endif // #ifndef BOOST_HASH_IS_TUPLE_LIKE_HPP_INCLUDED
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 7b2eccc..bd6efa0 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -117,3 +117,5 @@ run hash_is_avalanching_test.cpp ;
 run hash_is_avalanching_test2.cpp ;
 
 run hash_nullptr_test.cpp ;
+
+run is_tuple_like_test.cpp ;
diff --git a/test/is_tuple_like_test.cpp b/test/is_tuple_like_test.cpp
new file mode 100644
index 0000000..553d6ca
--- /dev/null
+++ b/test/is_tuple_like_test.cpp
@@ -0,0 +1,86 @@
+// Copyright 2017, 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/container_hash/is_tuple_like.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <boost/config.hpp>
+#include <utility>
+
+struct X
+{
+};
+
+#if !defined(BOOST_NO_CXX11_HDR_TUPLE)
+
+#include <tuple>
+
+namespace user
+{
+
+struct Y
+{
+    int a;
+    int b;
+};
+
+template<std::size_t I> int& get( Y& v );
+template<std::size_t I> int const& get( Y const& v );
+
+template<> int& get<0>( Y& v )
+{
+    return v.a;
+}
+
+template<> int const& get<0>( Y const& v )
+{
+    return v.a;
+}
+
+template<> int& get<1>( Y& v )
+{
+    return v.b;
+}
+
+template<> int const& get<1>( Y const& v )
+{
+    return v.b;
+}
+
+} // namespace user
+
+namespace std
+{
+
+template<> struct tuple_size<user::Y>: std::integral_constant<std::size_t, 2>
+{
+};
+
+} // namespace std
+
+#endif // #if !defined(BOOST_NO_CXX11_HDR_TUPLE)
+
+int main()
+{
+    using boost::container_hash::is_tuple_like;
+
+    BOOST_TEST_TRAIT_FALSE((is_tuple_like<void>));
+    BOOST_TEST_TRAIT_FALSE((is_tuple_like<int>));
+    BOOST_TEST_TRAIT_FALSE((is_tuple_like<X>));
+    BOOST_TEST_TRAIT_FALSE((is_tuple_like<int[2]>));
+
+#if !defined(BOOST_NO_CXX11_HDR_TUPLE)
+
+    BOOST_TEST_TRAIT_TRUE((is_tuple_like< std::pair<int, X> >));
+
+    BOOST_TEST_TRAIT_TRUE((is_tuple_like< std::tuple<> >));
+    BOOST_TEST_TRAIT_TRUE((is_tuple_like< std::tuple<X> >));
+    BOOST_TEST_TRAIT_TRUE((is_tuple_like< std::tuple<X, X> >));
+    BOOST_TEST_TRAIT_TRUE((is_tuple_like< std::tuple<X, X, X> >));
+
+    BOOST_TEST_TRAIT_TRUE((is_tuple_like<user::Y>));
+
+#endif
+
+    return boost::report_errors();
+}