libcruft-util/tuple/index.hpp

127 lines
3.6 KiB
C++
Raw Normal View History

/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2018 Danny Robson <danny@nerdcruft.net>
*/
#ifndef CRUFT_UTIL_TUPLE_INDEX_HPP
#define CRUFT_UTIL_TUPLE_INDEX_HPP
#include <cstddef>
///////////////////////////////////////////////////////////////////////////
// the implementation of all the below must be standalone as they are a
// potential building block in other algorithms and we can't be sure we
// won't create a dependency loop somewhere.
namespace util::tuple::index {
///////////////////////////////////////////////////////////////////////////
template <size_t ...Indices>
struct indices {};
///////////////////////////////////////////////////////////////////////////
template <typename A, typename B>
struct cat;
//-------------------------------------------------------------------------
template <
size_t ...A,
size_t ...B
>
struct cat<
indices<A...>,
indices<B...>
> {
using type = indices<A..., B...>;
};
//-------------------------------------------------------------------------
template <typename A, typename B>
using cat_t = typename cat<A,B>::type;
///////////////////////////////////////////////////////////////////////////
namespace detail {
template <size_t N>
struct make_indices {
using type = cat_t<
typename make_indices<N-1>::type,
indices<N-1>
>;
};
template <>
struct make_indices<0> {
using type = indices<>;
};
};
//-------------------------------------------------------------------------
// create a monotonically increasing index sequence over the range [0,N)
template <size_t N>
struct make_indices {
using type = typename detail::make_indices<N>::type;
};
//-------------------------------------------------------------------------
template <size_t N>
using make_indices_t = typename make_indices<N>::type;
///////////////////////////////////////////////////////////////////////////
namespace detail {
template <typename Indices>
struct make_reverse;
template <size_t Head, size_t ...Tail>
struct make_reverse<
indices<Head,Tail...>
> {
using type = cat_t<
typename make_reverse<indices<Tail...>>::type,
indices<Head>
>;
};
template <>
struct make_reverse<
indices<>
> {
using type = indices<>;
};
};
//-------------------------------------------------------------------------
// create a montonically decreasing index sequence over the range (N-1, 0].
//
// eg, make_reverse<3> is indices<3,2,1,0>
template <size_t N>
struct make_reverse {
using type = typename detail::make_reverse<
make_indices_t<N>
>::type;
};
//-------------------------------------------------------------------------
template <size_t N>
using make_reverse_t = typename make_reverse<N>::type;
};
#endif