acceptable_types.h

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/*
 * Copyright 2026 MusicScience37 (Kenta Kabashima)
 *
 * 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.
 */
#pragma once
 
#include <type_traits>
 
#include "func_sketch/math/common_type.h"
 
namespace func_sketch::math {

struct NoAcceptableType {};
 
namespace details {

template <typename ReceivedType, typename... AcceptableTypes>
struct SelectTypeToUseImpl;

template <typename ReceivedType, typename FirstAcceptableType,
    typename... RemainingAcceptableTypes>
struct SelectTypeToUseImpl<ReceivedType, FirstAcceptableType,
    RemainingAcceptableTypes...> {
    using Type = std::conditional_t<
        std::is_same_v<CommonType<ReceivedType, FirstAcceptableType>,
            FirstAcceptableType>,
        FirstAcceptableType,
        typename SelectTypeToUseImpl<ReceivedType,
            RemainingAcceptableTypes...>::Type>;
};

template <typename ReceivedType>
struct SelectTypeToUseImpl<ReceivedType> {
    using Type = NoAcceptableType;
};
 
}  // namespace details

template <typename... Types>
struct AcceptableTypes {
    template <typename ReceivedType>
    using SelectTypeToUse =
        details::SelectTypeToUseImpl<ReceivedType, Types...>::Type;
};
 
namespace details {

template <typename Type>
struct IsAcceptableTypes : std::false_type {};

template <typename... Types>
struct IsAcceptableTypes<AcceptableTypes<Types...>> : std::true_type {};
 
}  // namespace details

template <typename Type>
concept AcceptableTypesSpec = details::IsAcceptableTypes<Type>::value;
 
}  // namespace func_sketch::math