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Diffstat (limited to 'boost/hana/is_empty.hpp')
-rw-r--r-- | boost/hana/is_empty.hpp | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/boost/hana/is_empty.hpp b/boost/hana/is_empty.hpp new file mode 100644 index 0000000000..ac1051914b --- /dev/null +++ b/boost/hana/is_empty.hpp @@ -0,0 +1,45 @@ +/*! +@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 |