// 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 #if defined(_MSC_VER) #pragma warning( disable: 4244 ) // 'initializing': conversion from 'int' to 'char', possible loss of data #endif #include #include // Technically std::tuple isn't constexpr enabled in C++11, but it works with libstdc++ #if defined( BOOST_MP11_NO_CONSTEXPR ) || ( !defined( __GLIBCXX__ ) && __cplusplus < 201400L ) int main() {} #else #include #include #include struct T1 { int x, y, z; constexpr T1( int x = 0, int y = 0, int z = 0 ): x(x), y(y), z(z) {} }; int main() { using boost::mp11::construct_from_tuple; { constexpr std::tuple tp{ 1, 2, 3 }; constexpr auto r = construct_from_tuple( tp ); static_assert( r.x == 1, "r.x == 1" ); static_assert( r.y == 2, "r.y == 2" ); static_assert( r.z == 3, "r.z == 3" ); } { constexpr std::pair tp{ 1, 2 }; constexpr auto r = construct_from_tuple( tp ); static_assert( r.x == 1, "r.x == 1" ); static_assert( r.y == 2, "r.y == 2" ); static_assert( r.z == 0, "r.z == 0" ); } { constexpr std::array tp{{ 1, 2, 3 }}; constexpr auto r = construct_from_tuple( tp ); static_assert( r.x == 1, "r.x == 1" ); static_assert( r.y == 2, "r.y == 2" ); static_assert( r.z == 3, "r.z == 3" ); } #if defined( __clang_major__ ) && __clang_major__ == 3 && __clang_minor__ < 9 // "error: default initialization of an object of const type 'const std::tuple<>' without a user-provided default constructor" #else { constexpr std::tuple<> tp; constexpr auto r = construct_from_tuple( tp ); static_assert( r.x == 0, "r.x == 0" ); static_assert( r.y == 0, "r.y == 0" ); static_assert( r.z == 0, "r.z == 0" ); } #endif } #endif