Edit: /usr/include/boost/hana/empty.hpp (1400B)
/*!
@file
Defines `boost::hana::empty`.
@copyright Louis Dionne 2013-2017
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_EMPTY_HPP
#define BOOST_HANA_EMPTY_HPP
#include
#include
#include
#include
#include
#include
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template
constexpr auto empty_t::operator()() const {
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::MonadPlus::value,
"hana::empty() requires 'M' to be a MonadPlus");
#endif
using Empty = BOOST_HANA_DISPATCH_IF(empty_impl,
hana::MonadPlus::value
);
return Empty::apply();
}
//! @endcond
template
struct empty_impl> : default_ {
template
static constexpr auto apply(Args&& ...) = delete;
};
template
struct empty_impl::value>> {
static constexpr auto apply() {
return hana::make();
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_EMPTY_HPP