51 lines
1.5 KiB
C++
51 lines
1.5 KiB
C++
|
/*!
|
||
|
|
@file
|
||
|
|
Defines `boost::hana::chain`.
|
||
|
|
|
||
|
|
@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_CHAIN_HPP
|
||
|
|
#define BOOST_HANA_CHAIN_HPP
|
||
|
|
|
||
|
|
#include <boost/hana/fwd/chain.hpp>
|
||
|
|
|
||
|
|
#include <boost/hana/concept/monad.hpp>
|
||
|
|
#include <boost/hana/config.hpp>
|
||
|
|
#include <boost/hana/core/dispatch.hpp>
|
||
|
|
#include <boost/hana/flatten.hpp>
|
||
|
|
#include <boost/hana/transform.hpp>
|
||
|
|
|
||
|
|
|
||
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
||
|
|
//! @cond
|
||
|
|
template <typename Xs, typename F>
|
||
|
|
constexpr decltype(auto) chain_t::operator()(Xs&& xs, F&& f) const {
|
||
|
|
using M = typename hana::tag_of<Xs>::type;
|
||
|
|
using Chain = BOOST_HANA_DISPATCH_IF(chain_impl<M>,
|
||
|
|
hana::Monad<M>::value
|
||
|
|
);
|
||
|
|
|
||
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
||
|
|
static_assert(hana::Monad<M>::value,
|
||
|
|
"hana::chain(xs, f) requires 'xs' to be a Monad");
|
||
|
|
#endif
|
||
|
|
|
||
|
|
return Chain::apply(static_cast<Xs&&>(xs), static_cast<F&&>(f));
|
||
|
|
}
|
||
|
|
//! @endcond
|
||
|
|
|
||
|
|
template <typename M, bool condition>
|
||
|
|
struct chain_impl<M, when<condition>> : default_ {
|
||
|
|
template <typename Xs, typename F>
|
||
|
|
static constexpr auto apply(Xs&& xs, F&& f) {
|
||
|
|
return hana::flatten(hana::transform(static_cast<Xs&&>(xs),
|
||
|
|
static_cast<F&&>(f)));
|
||
|
|
}
|
||
|
|
};
|
||
|
|
BOOST_HANA_NAMESPACE_END
|
||
|
|
|
||
|
|
#endif // !BOOST_HANA_CHAIN_HPP
|