Unique.hpp

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/* Copyright 2022 Benjamin Worpitz, Bernhard Manfred Gruber
 * SPDX-License-Identifier: MPL-2.0
 */
 
#pragma once
 
#include <type_traits>
 
namespace alpaka::meta
{
    namespace detail
    {
        template<typename T, typename... Ts>
        struct UniqueHelper
        {
            using type = T;
        };
 
        template<template<typename...> class TList, typename... Ts, typename U, typename... Us>
        struct UniqueHelper<TList<Ts...>, U, Us...>
            : std::conditional_t<
                  (std::is_same_v<U, Ts> || ...),
                  UniqueHelper<TList<Ts...>, Us...>,
                  UniqueHelper<TList<Ts..., U>, Us...>>
        {
        };
 
        template<typename T>
        struct UniqueImpl;
 
        template<template<typename...> class TList, typename... Ts>
        struct UniqueImpl<TList<Ts...>>
        {
            using type = typename UniqueHelper<TList<>, Ts...>::type;
        };
    } // namespace detail
 
    //! Trait that returns a list with only unique (no equal) types (a set). Duplicates will be filtered out.
    template<typename TList>
    using Unique = typename detail::UniqueImpl<TList>::type;
} // namespace alpaka::meta