customisation_point.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 <utility>
 
#include <seqan3/core/platform.hpp>
 
namespace seqan3::detail
{
 
// ============================================================================
// priority_tag
// ============================================================================

template <size_t I>
struct priority_tag
    // Doxygen fail
    : priority_tag<I - 1>
{};

template <>
struct priority_tag<0>
{};
 
} // namespace seqan3::detail
 
// ============================================================================
// SEQAN3_CPO_OVERLOAD
// ============================================================================
#if SEQAN3_DOXYGEN_ONLY(1) 0
#    define SEQAN3_CPO_OVERLOAD_BODY(...)                                                                              \
        noexcept(auto)                                                                                                 \
        {                                                                                                              \
            return __VA_ARGS__;                                                                                        \
        }
#else // ^^^ (simplified) doxygen version / normal definition vvv
#    define SEQAN3_CPO_OVERLOAD_BODY(...)                                                                              \
        noexcept(noexcept(__VA_ARGS__))->decltype(__VA_ARGS__)                                                         \
        {                                                                                                              \
            return __VA_ARGS__;                                                                                        \
        }                                                                                                              \
        static_assert(true)
#endif

#define SEQAN3_CPO_OVERLOAD(...) cpo_overload(__VA_ARGS__) SEQAN3_CPO_OVERLOAD_BODY
 
namespace seqan3::detail
{
template <typename derived_t, unsigned max_priority>
struct customisation_point_object
{
private:
    friend derived_t;
 
    constexpr customisation_point_object() = default;                                               
    constexpr customisation_point_object(customisation_point_object &&) = default;                  
    constexpr customisation_point_object(customisation_point_object const &) = default;             
    constexpr customisation_point_object & operator=(customisation_point_object &&) = default;      
    constexpr customisation_point_object & operator=(customisation_point_object const &) = default; 
 
public:
    template <typename... args_t, typename derived_type = derived_t /*circumvent incomplete types*/>
    constexpr auto operator()(args_t &&... args) const SEQAN3_CPO_OVERLOAD_BODY(
        /*return*/ derived_type::cpo_overload(priority_tag<max_priority>{}, std::forward<args_t>(args)...) /*;*/
    );
};
} // namespace seqan3::detail