Edit: /usr/include/boost/hana/prepend.hpp (2372B)
/*!
@file
Defines `boost::hana::prepend`.
@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_PREPEND_HPP
#define BOOST_HANA_PREPEND_HPP
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template
constexpr auto prepend_t::operator()(Xs&& xs, X&& x) const {
using M = typename hana::tag_of::type;
using Prepend = BOOST_HANA_DISPATCH_IF(prepend_impl,
hana::MonadPlus::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::MonadPlus::value,
"hana::prepend(xs, x) requires 'xs' to be a MonadPlus");
#endif
return Prepend::apply(static_cast(xs), static_cast(x));
}
//! @endcond
template
struct prepend_impl> : default_ {
template
static constexpr auto apply(Xs&& xs, X&& x) {
return hana::concat(hana::lift(static_cast(x)),
static_cast(xs));
}
};
template
struct prepend_impl::value>> {
template
static constexpr auto prepend_helper(Xs&& xs, X&& x, std::index_sequence) {
return hana::make(
static_cast(x), hana::at_c(static_cast(xs))...
);
}
template
static constexpr auto apply(Xs&& xs, X&& x) {
constexpr std::size_t N = decltype(hana::length(xs))::value;
return prepend_helper(static_cast(xs), static_cast(x),
std::make_index_sequence{});
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_PREPEND_HPP