function_traits.hpp

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// SPDX-FileCopyrightText: 2006-2025 Knut Reinert & Freie Universität Berlin
// SPDX-FileCopyrightText: 2016-2025 Knut Reinert & MPI für molekulare Genetik
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
#include <functional>
 
#include <seqan3/utility/type_pack/traits.hpp>
 
namespace seqan3
{
 
template <typename function_t>
struct function_traits;
 
template <typename return_t, typename... args_t>
struct function_traits<std::function<return_t(args_t...)>>
{
    static constexpr size_t argument_count = sizeof...(args_t);
 
    using result_type = return_t;
 
    template <size_t index>
        requires (index < argument_count)
    using argument_type_at = pack_traits::at<index, args_t...>;
};
 
// Overload for all function types.
template <typename function_t>
    requires requires (function_t fn) {
        { std::function{fn} };
    }
struct function_traits<function_t> : function_traits<decltype(std::function{std::declval<function_t>()})>
{};
 
} // namespace seqan3