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#pragma once
/* Copyright (c) 2017 Stanislaw Halik
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*/
#define OTR_META_INST_FAIL(x) \
static_assert(sizeof...(x) == ~0ul); \
static_assert(sizeof...(x) == 0u)
namespace meta::detail {
template<typename... xs>
struct tuple;
template<typename... xs>
struct reverse_
{
OTR_META_INST_FAIL(xs);
};
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... xs>
struct lift_
{
OTR_META_INST_FAIL(xs);
};
template<template<typename...> class to, template<typename...> class from, typename... xs>
struct lift_<to, from<xs...>>
{
using type = to<xs...>;
};
} // ns meta::detail
namespace meta {
template<typename... xs>
using reverse = typename detail::reverse_<detail::tuple<xs...>, detail::tuple<>>::type;
// the to/from order is awkward but mimics function composition
template<template<typename...> class to, typename from>
using lift = typename detail::lift_<to, from>::type;
template<typename x, typename... xs>
using first = x;
template<typename x, typename... xs>
using rest = detail::tuple<xs...>;
template<typename... xs>
using butlast = reverse<rest<reverse<xs...>>>;
template<typename... xs>
using last = lift<first, reverse<xs...>>;
} // ns meta
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