function_traits.hpp

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// -----------------------------------------------------------------------------------------------------
// Copyright (c) 2006-2021, Knut Reinert & Freie Universität Berlin
// Copyright (c) 2016-2021, Knut Reinert & MPI für molekulare Genetik
// This file may be used, modified and/or redistributed under the terms of the 3-clause BSD-License
// shipped with this file and also available at: https://github.com/seqan/seqan3/blob/master/LICENSE.md
// -----------------------------------------------------------------------------------------------------
 
#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