integersequence.h

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// SPDX-FileCopyrightText: Copyright (C) 2016 swift Project Community / Contributors
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-swift-pilot-client-1
 
 
#ifndef SWIFT_MISC_INTEGERSEQUENCE_H
#define SWIFT_MISC_INTEGERSEQUENCE_H
 
#include <cstddef>
 
namespace swift::misc::private_ns
{
 
    // Remove elements from an index_sequence for which a pack parameter fails to satisfy a given predicate.
    template <typename, typename T, bool...>
    struct MaskSequenceImpl
    {
        using type = T;
    };
 
    template <size_t I, size_t... Is, bool... Mask, size_t... Js>
    struct MaskSequenceImpl<std::index_sequence<I, Is...>, std::index_sequence<Js...>, true, Mask...>
    {
        using type =
            typename MaskSequenceImpl<std::index_sequence<Is...>, std::index_sequence<Js..., I>, Mask...>::type;
    };
 
    template <size_t I, size_t... Is, bool... Mask, size_t... Js>
    struct MaskSequenceImpl<std::index_sequence<I, Is...>, std::index_sequence<Js...>, false, Mask...>
    {
        using type = typename MaskSequenceImpl<std::index_sequence<Is...>, std::index_sequence<Js...>, Mask...>::type;
    };
 
    template <typename Seq, bool... Mask>
    using MaskSequence = typename MaskSequenceImpl<Seq, std::index_sequence<>, Mask...>::type;
 
} // namespace swift::misc::private_ns
 
#endif // SWIFT_MISC_INTEGERSEQUENCE_H