Filter.hpp

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/* Copyright 2022 Benjamin Worpitz, Bernhard Manfred Gruber
 * SPDX-License-Identifier: MPL-2.0
 */
 
#pragma once
 
#include "alpaka/meta/Concatenate.hpp"
 
#include <type_traits>
 
namespace alpaka::meta
{
    namespace detail
    {
        template<template<typename...> class TList, template<typename...> class TPred, typename... Ts>
        struct FilterImplHelper;
 
        template<template<typename...> class TList, template<typename...> class TPred>
        struct FilterImplHelper<TList, TPred>
        {
            using type = TList<>;
        };
 
        template<template<typename...> class TList, template<typename...> class TPred, typename T, typename... Ts>
        struct FilterImplHelper<TList, TPred, T, Ts...>
        {
            using type = std::conditional_t<
                TPred<T>::value,
                Concatenate<TList<T>, typename FilterImplHelper<TList, TPred, Ts...>::type>,
                typename FilterImplHelper<TList, TPred, Ts...>::type>;
        };
 
        template<typename TList, template<typename...> class TPred>
        struct FilterImpl;
 
        template<template<typename...> class TList, template<typename...> class TPred, typename... Ts>
        struct FilterImpl<TList<Ts...>, TPred>
        {
            using type = typename detail::FilterImplHelper<TList, TPred, Ts...>::type;
        };
    } // namespace detail
 
    /// \tparam TPred Only the first parameter is used, all other must be set by TPred to some default.
    ///               Using '...' instead of a single type is a workaround for CrayClang.
    template<typename TList, template<typename...> class TPred>
    using Filter = typename detail::FilterImpl<TList, TPred>::type;
} // namespace alpaka::meta