/*! @file Defines `boost::hana::is_empty`. @copyright Louis Dionne 2013-2016 Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) */ #ifndef BOOST_HANA_IS_EMPTY_HPP #define BOOST_HANA_IS_EMPTY_HPP #include <boost/hana/fwd/is_empty.hpp> #include <boost/hana/concept/iterable.hpp> #include <boost/hana/config.hpp> #include <boost/hana/core/dispatch.hpp> BOOST_HANA_NAMESPACE_BEGIN //! @cond template <typename Xs> constexpr auto is_empty_t::operator()(Xs const& xs) const { using It = typename hana::tag_of<Xs>::type; using IsEmpty = BOOST_HANA_DISPATCH_IF(is_empty_impl<It>, hana::Iterable<It>::value ); #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS static_assert(hana::Iterable<It>::value, "hana::is_empty(xs) requires 'xs' to be an Iterable"); #endif return IsEmpty::apply(xs); } //! @endcond template <typename It, bool condition> struct is_empty_impl<It, when<condition>> : default_ { template <typename ...Args> static constexpr auto apply(Args&& ...) = delete; }; BOOST_HANA_NAMESPACE_END #endif // !BOOST_HANA_IS_EMPTY_HPP