Edit: /usr/include/boost/hana/unpack.hpp (5175B)
/*!
@file
Defines `boost::hana::unpack`.
@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_UNPACK_HPP
#define BOOST_HANA_UNPACK_HPP
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template
constexpr decltype(auto) unpack_t::operator()(Xs&& xs, F&& f) const {
using S = typename hana::tag_of::type;
using Unpack = BOOST_HANA_DISPATCH_IF(unpack_impl,
hana::Foldable::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Foldable::value,
"hana::unpack(xs, f) requires 'xs' to be Foldable");
#endif
return Unpack::apply(static_cast(xs), static_cast(f));
}
//! @endcond
template
struct unpack_impl> : default_ {
template
static constexpr decltype(auto) apply(Xs&& xs, F&& f) {
return hana::fold_left(static_cast(xs),
static_cast(f),
hana::partial)();
}
};
template
struct unpack_impl::value && !is_default>::value
>> {
template
static constexpr decltype(auto)
unpack_helper(Xs&& xs, F&& f, std::index_sequence) {
return static_cast(f)(hana::at_c(static_cast(xs))...);
}
template
static constexpr decltype(auto) apply(Xs&& xs, F&& f) {
constexpr std::size_t N = decltype(hana::length(xs))::value;
return unpack_helper(static_cast(xs), static_cast(f),
std::make_index_sequence{});
}
};
template
struct unpack_impl {
template
static constexpr decltype(auto)
unpack_helper(Xs&& xs, F&& f, std::index_sequence) {
return static_cast(f)(static_cast(xs)[i]...);
}
template
static constexpr decltype(auto) apply(Xs&& xs, F&& f) {
return unpack_impl::unpack_helper(static_cast(xs),
static_cast(f),
std::make_index_sequence{});
}
};
//////////////////////////////////////////////////////////////////////////
// Model for Products
//////////////////////////////////////////////////////////////////////////
template
struct unpack_impl::value>> {
template
static constexpr decltype(auto) apply(P&& p, F&& f) {
return static_cast(f)(
hana::first(static_cast(p)),
hana::second(static_cast(p))
);
}
};
//////////////////////////////////////////////////////////////////////////
// Model for Structs
//////////////////////////////////////////////////////////////////////////
namespace struct_detail {
// This is equivalent to `demux`, except that `demux` can't forward
// the `udt` because it does not know the `g`s are accessors. Hence,
// this can result in faster code.
struct almost_demux {
template
constexpr decltype(auto)
operator()(F&& f, Udt&& udt, Members&& ...g) const {
return static_cast(f)(hana::make_pair(
hana::first(static_cast(g)),
hana::second(static_cast(g))
(static_cast(udt))
)...);
}
};
}
template
struct unpack_impl::value>> {
template
static constexpr decltype(auto) apply(Udt&& udt, F&& f) {
return hana::unpack(hana::accessors(),
hana::partial(struct_detail::almost_demux{},
static_cast(f),
static_cast(udt)));
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_UNPACK_HPP