Add tuple_apply

test/tuple_apply_cx.cpp

@@ -0,0 +1,66 @@
+
+//  Copyright 2015 Peter Dimov.
+//
+// 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
+
+#include <boost/mp11/tuple.hpp>
+#include <boost/config.hpp>
+
+// Technically std::tuple isn't constexpr enabled in C++11, but it works with libstdc++
+
+#if defined( BOOST_NO_CXX11_CONSTEXPR ) || ( defined( _LIBCPP_VERSION ) && __cplusplus < 201400L )
+
+int main() {}
+
+#else
+
+#include <tuple>
+#include <array>
+#include <utility>
+
+constexpr int f( int x, int y, int z )
+{
+    return x * 100 + y * 10 + z;
+}
+
+constexpr int g( int x, int y )
+{
+    return x * 10 + y;
+}
+
+constexpr int h()
+{
+    return 11;
+}
+
+int main()
+{
+    {
+        constexpr std::tuple<int, short, char> tp{ 1, 2, 3 };
+        constexpr auto r = boost::mp11::tuple_apply( f, tp );
+        static_assert( r == 123, "r == 123" );
+    }
+
+    {
+        constexpr std::pair<short, char> tp{ 1, 2 };
+        constexpr auto r = boost::mp11::tuple_apply( g, tp );
+        static_assert( r == 12, "r == 12" );
+    }
+
+    {
+        constexpr std::array<short, 3> tp{{ 1, 2, 3 }};
+        constexpr auto r = boost::mp11::tuple_apply( f, tp );
+        static_assert( r == 123, "r == 123" );
+    }
+
+    {
+        constexpr std::tuple<> tp;
+        constexpr auto r = boost::mp11::tuple_apply( h, tp );
+        static_assert( r == 11, "r == 11" );
+    }
+}
+
+#endif