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/*!
@file
Adapts `std::tuple` for use with Hana.
@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_EXT_STD_TUPLE_HPP
#define BOOST_HANA_EXT_STD_TUPLE_HPP
#include <boost/hana/bool.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/detail/decay.hpp>
#include <boost/hana/fwd/at.hpp>
#include <boost/hana/fwd/core/make.hpp>
#include <boost/hana/fwd/core/tag_of.hpp>
#include <boost/hana/fwd/drop_front.hpp>
#include <boost/hana/fwd/empty.hpp>
#include <boost/hana/fwd/flatten.hpp>
#include <boost/hana/fwd/front.hpp>
#include <boost/hana/fwd/is_empty.hpp>
#include <boost/hana/fwd/length.hpp>
#include <boost/hana/fwd/lift.hpp>
#include <boost/hana/integral_constant.hpp>
#include <cstddef>
#include <tuple>
#include <type_traits>
#include <utility>
#ifdef BOOST_HANA_CONFIG_HAS_NO_STD_TUPLE_ADAPTER
# error The adapter for std::tuple is not supported with versions of \
libc++ prior to the one shipped with Clang 3.7 because of a bug \
in the tuple implementation.
#endif
#ifdef BOOST_HANA_DOXYGEN_INVOKED
namespace std {
//! @ingroup group-ext-std
//! Adapter for `std::tuple`s.
//!
//!
//! Modeled concepts
//! ----------------
//! A `std::tuple` is a model of the `Sequence` concept, and all the
//! concepts it refines. That makes it essentially the same as a Hana
//! tuple, although the complexity of some operations might differ from
//! that of Hana's tuple.
//!
//! @include example/ext/std/tuple.cpp
template <typename ...T>
struct tuple { };
}
#endif
BOOST_HANA_NAMESPACE_BEGIN
namespace ext { namespace std { struct tuple_tag; }}
template <typename ...Xs>
struct tag_of<std::tuple<Xs...>> {
using type = ext::std::tuple_tag;
};
//////////////////////////////////////////////////////////////////////////
// make
//////////////////////////////////////////////////////////////////////////
template <>
struct make_impl<ext::std::tuple_tag> {
template <typename ...Xs>
static constexpr decltype(auto) apply(Xs&& ...xs) {
return std::make_tuple(static_cast<Xs&&>(xs)...);
}
};
//////////////////////////////////////////////////////////////////////////
// Applicative
//////////////////////////////////////////////////////////////////////////
template <>
struct lift_impl<ext::std::tuple_tag> {
template <typename X>
static constexpr auto apply(X&& x) {
return std::tuple<typename detail::decay<X>::type>{
static_cast<X&&>(x)};
}
};
//////////////////////////////////////////////////////////////////////////
// Monad
//////////////////////////////////////////////////////////////////////////
template <>
struct flatten_impl<ext::std::tuple_tag> {
template <typename Xs, std::size_t ...i>
static constexpr decltype(auto)
flatten_helper(Xs&& xs, std::index_sequence<i...>) {
#if defined(BOOST_HANA_CONFIG_LIBCPP_HAS_BUG_22806)
return std::tuple_cat(std::get<i>(xs)...);
#else
return std::tuple_cat(std::get<i>(static_cast<Xs&&>(xs))...);
#endif
}
template <typename Xs>
static constexpr decltype(auto) apply(Xs&& xs) {
using Raw = typename std::remove_reference<Xs>::type;
constexpr std::size_t Length = std::tuple_size<Raw>::value;
return flatten_helper(static_cast<Xs&&>(xs),
std::make_index_sequence<Length>{});
}
};
//////////////////////////////////////////////////////////////////////////
// MonadPlus
//////////////////////////////////////////////////////////////////////////
template <>
struct empty_impl<ext::std::tuple_tag> {
static constexpr auto apply()
{ return std::tuple<>{}; }
};
//////////////////////////////////////////////////////////////////////////
// Iterable
//////////////////////////////////////////////////////////////////////////
template <>
struct front_impl<ext::std::tuple_tag> {
template <typename Xs>
static constexpr decltype(auto) apply(Xs&& xs) {
return std::get<0>(static_cast<Xs&&>(xs));
}
};
template <>
struct drop_front_impl<ext::std::tuple_tag> {
template <std::size_t n, typename Xs, std::size_t ...i>
static constexpr auto drop_front_helper(Xs&& xs, std::index_sequence<i...>) {
return std::make_tuple(
hana::at_c<n + i>(static_cast<Xs&&>(xs))...
);
}
template <typename Xs, typename N>
static constexpr auto apply(Xs&& xs, N const&) {
using Raw = typename std::remove_reference<Xs>::type;
constexpr std::size_t n = N::value;
constexpr auto len = std::tuple_size<Raw>::value;
return drop_front_helper<n>(static_cast<Xs&&>(xs),
std::make_index_sequence<(n < len ? len - n : 0)>{});
}
};
template <>
struct is_empty_impl<ext::std::tuple_tag> {
template <typename ...Xs>
static constexpr auto apply(std::tuple<Xs...> const&)
{ return hana::bool_c<sizeof...(Xs) == 0>; }
};
template <>
struct at_impl<ext::std::tuple_tag> {
template <typename Xs, typename N>
static constexpr decltype(auto) apply(Xs&& xs, N const&) {
constexpr std::size_t index = N::value;
return std::get<index>(static_cast<Xs&&>(xs));
}
};
//////////////////////////////////////////////////////////////////////////
// Foldable
//////////////////////////////////////////////////////////////////////////
template <>
struct length_impl<ext::std::tuple_tag> {
template <typename ...Xs>
static constexpr auto apply(std::tuple<Xs...> const&) {
return hana::size_c<sizeof...(Xs)>;
}
};
//////////////////////////////////////////////////////////////////////////
// Sequence
//////////////////////////////////////////////////////////////////////////
template <>
struct Sequence<ext::std::tuple_tag> {
static constexpr bool value = true;
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_EXT_STD_TUPLE_HPP
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