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