/*!
|
@file
|
Defines `boost::hana::flatten`.
|
|
@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_FLATTEN_HPP
|
#define BOOST_HANA_FLATTEN_HPP
|
|
#include <boost/hana/fwd/flatten.hpp>
|
|
#include <boost/hana/concept/monad.hpp>
|
#include <boost/hana/concept/sequence.hpp>
|
#include <boost/hana/config.hpp>
|
#include <boost/hana/core/dispatch.hpp>
|
#include <boost/hana/core/make.hpp>
|
#include <boost/hana/detail/unpack_flatten.hpp>
|
#include <boost/hana/functional/id.hpp>
|
#include <boost/hana/fwd/chain.hpp>
|
|
#include <cstddef>
|
#include <utility>
|
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
//! @cond
|
template <typename Xs>
|
constexpr auto flatten_t::operator()(Xs&& xs) const {
|
using M = typename hana::tag_of<Xs>::type;
|
using Flatten = BOOST_HANA_DISPATCH_IF(flatten_impl<M>,
|
hana::Monad<M>::value
|
);
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
static_assert(hana::Monad<M>::value,
|
"hana::flatten(xs) requires 'xs' to be a Monad");
|
#endif
|
|
return Flatten::apply(static_cast<Xs&&>(xs));
|
}
|
//! @endcond
|
|
template <typename M, bool condition>
|
struct flatten_impl<M, when<condition>> : default_ {
|
template <typename Xs>
|
static constexpr auto apply(Xs&& xs)
|
{ return hana::chain(static_cast<Xs&&>(xs), hana::id); }
|
};
|
|
template <typename S>
|
struct flatten_impl<S, when<Sequence<S>::value>> {
|
template <typename Xs>
|
static constexpr auto apply(Xs&& xs) {
|
return detail::unpack_flatten(static_cast<Xs&&>(xs), hana::make<S>);
|
}
|
};
|
BOOST_HANA_NAMESPACE_END
|
|
#endif // !BOOST_HANA_FLATTEN_HPP
|
