FM / std

/usr/include/boost/hana/ext/std

Name	Size	Mode	Actions
array.hpp	6306	0644	edit dl rm
integer_sequence.hpp	5292	0644	edit dl rm
integral_constant.hpp	2975	0644	edit dl rm
pair.hpp	2687	0644	edit dl rm
ratio.hpp	5736	0644	edit dl rm
tuple.hpp	6118	0644	edit dl rm
vector.hpp	3907	0644	edit dl rm

Edit: /usr/include/boost/hana/ext/std/array.hpp (6306B)

/*!
@file
Adapts `std::array` for use with Hana.

@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_EXT_STD_ARRAY_HPP
#define BOOST_HANA_EXT_STD_ARRAY_HPP

#include <boost/hana/bool.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/detail/algorithm.hpp>
#include <boost/hana/fwd/at.hpp>
#include <boost/hana/fwd/core/tag_of.hpp>
#include <boost/hana/fwd/drop_front.hpp>
#include <boost/hana/fwd/equal.hpp>
#include <boost/hana/fwd/is_empty.hpp>
#include <boost/hana/fwd/length.hpp>
#include <boost/hana/fwd/less.hpp>
#include <boost/hana/integral_constant.hpp>

#include <array>
#include <cstddef>
#include <type_traits>
#include <utility>

#ifdef BOOST_HANA_DOXYGEN_INVOKED
namespace std {
    //! @ingroup group-ext-std
    //! Adaptation of `std::array` for Hana.
    //!
    //!
    //!
    //! Modeled concepts
    //! ----------------
    //! 1. `Comparable`\n
    //! `std::array`s are compared as per `std::equal`, except that two arrays
    //! with different sizes compare unequal instead of triggering an error
    //! and the result of the comparison is `constexpr` if both arrays are
    //! `constexpr`.
    //! @include example/ext/std/array/comparable.cpp
    //!
    //! 2. `Orderable`\n
    //! `std::array`s are ordered with the usual lexicographical ordering,
    //! except that two arrays with different size can be ordered instead
    //! of triggering an error and the result of the comparison is `constexpr`
    //! if both arrays are `constexpr`.
    //! @include example/ext/std/array/orderable.cpp
    //!
    //! 3. `Foldable`\n
    //! Folding an array from the left is equivalent to calling
    //! `std::accumulate` on it, except it can be `constexpr`.
    //! @include example/ext/std/array/foldable.cpp
    //!
    //! 4. `Iterable`\n
    //! Iterating over a `std::array` is equivalent to iterating over it with
    //! a normal `for` loop.
    //! @include example/ext/std/array/iterable.cpp
    template <typename T, std::size_t N>
    struct array { };
}
#endif

BOOST_HANA_NAMESPACE_BEGIN
    namespace ext { namespace std { struct array_tag; }}

template <typename T, std::size_t N>
    struct tag_of<std::array<T, N>> {
        using type = ext::std::array_tag;
    };

//////////////////////////////////////////////////////////////////////////
    // Foldable
    //////////////////////////////////////////////////////////////////////////
    template <>
    struct length_impl<ext::std::array_tag> {
        template <typename Xs>
        static constexpr auto apply(Xs const&) {
            return hana::size_c<std::tuple_size<Xs>::type::value>;
        }
    };

//////////////////////////////////////////////////////////////////////////
    // Iterable
    //////////////////////////////////////////////////////////////////////////
    template <>
    struct at_impl<ext::std::array_tag> {
        template <typename Xs, typename N>
        static constexpr decltype(auto) apply(Xs&& xs, N const&) {
            constexpr std::size_t n = N::value;
            return std::get<n>(static_cast<Xs&&>(xs));
        }
    };

template <>
    struct drop_front_impl<ext::std::array_tag> {
        template <std::size_t n, typename Xs, std::size_t ...i>
        static constexpr auto drop_front_helper(Xs&& xs, std::index_sequence<i...>) {
            using T = typename std::remove_reference<Xs>::type::value_type;
            return std::array<T, sizeof...(i)>{{static_cast<Xs&&>(xs)[n + i]...}};
        }

template <typename Xs, typename N>
        static constexpr auto apply(Xs&& xs, N const&) {
            constexpr std::size_t n = N::value;
            constexpr std::size_t len = std::tuple_size<
                typename std::remove_cv<
                    typename std::remove_reference<Xs>::type
                >::type
            >::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::array_tag> {
        template <typename T, std::size_t N>
        static constexpr auto apply(std::array<T, N> const&) {
            return hana::bool_c<N == 0>;
        }
    };

//////////////////////////////////////////////////////////////////////////
    // Comparable
    //////////////////////////////////////////////////////////////////////////
    template <>
    struct equal_impl<ext::std::array_tag, ext::std::array_tag> {
        template <typename T, std::size_t n, typename U>
        static constexpr bool apply(std::array<T, n> const& xs, std::array<U, n> const& ys)
        { return detail::equal(&xs[0], &xs[0] + n, &ys[0], &ys[0] + n); }

template <typename T, typename U>
        static constexpr auto apply(std::array<T, 0> const&, std::array<U, 0> const&)
        { return hana::true_c; }

template <typename T, std::size_t n, typename U, std::size_t m>
        static constexpr auto apply(std::array<T, n> const&, std::array<U, m> const&)
        { return hana::false_c; }
    };

//////////////////////////////////////////////////////////////////////////
    // Orderable
    //////////////////////////////////////////////////////////////////////////
    template <>
    struct less_impl<ext::std::array_tag, ext::std::array_tag> {
        template <typename T, std::size_t n, typename U, std::size_t m>
        static constexpr auto apply(std::array<T, n> const& xs, std::array<U, m> const& ys) {
            // This logic is more complex than it needs to be because we can't
            // use `.begin()` and `.end()`, which are not constexpr in C++14,
            // and because `&arr[0]` is UB when the array is empty.
            if (xs.empty()) {
                return !ys.empty();
            } else {
                if (ys.empty()) {
                    return false;
                } else {
                    return detail::lexicographical_compare(&xs[0], &xs[0] + n,
                                                           &ys[0], &ys[0] + m);
                }
            }
        }
    };
BOOST_HANA_NAMESPACE_END

#endif // !BOOST_HANA_EXT_STD_ARRAY_HPP

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