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#pragma once
#include <type_traits>
#include <tuple>
#include <cstddef>
namespace meta {
namespace detail {
template<typename x, typename y>
struct reverse_;
template<typename x0, typename... xs, template<typename...> class x, typename... ys>
struct reverse_<x<x0, xs...>, x<ys...>>
{
using type = typename reverse_<x<xs...>, x<x0, ys...>>::type;
};
template<template<typename...> class x, typename... ys>
struct reverse_<x<>, x<ys...>>
{
using type = x<ys...>;
};
template<template<typename...> class inst, typename x>
struct lift_;
template<template<typename...> class inst, template<typename...> class x, typename... xs>
struct lift_<inst, x<xs...>>
{
using type = inst<xs...>;
};
template<typename N, N max, N pos, typename... xs>
struct index_sequence_
{
using part = std::integral_constant<N, pos>;
using type = typename index_sequence_<N, max, pos+1, xs..., part>::type;
};
template<typename N, N max, typename... xs>
struct index_sequence_<N, max, max, xs...>
{
using type = std::tuple<xs...>;
};
} // ns detail
template<typename... xs>
using reverse = typename detail::reverse_<std::tuple<xs...>, std::tuple<>>::type;
template<template<typename...> class inst, class x>
using lift = typename detail::lift_<inst, x>::type;
template<typename x, typename... xs>
using first = x;
template<typename x, typename... xs>
using rest = std::tuple<xs...>;
template<typename... xs>
using butlast = reverse<rest<reverse<xs...>>>;
template<typename... xs>
using last = lift<first, reverse<xs...>>;
template<std::size_t max>
using index_sequence = typename detail::index_sequence_<std::size_t, max, std::size_t(0)>::type;
} // ns meta
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