customisation_point.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 <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>
{};
 
} // seqan3::detail
 
// ============================================================================
// SEQAN3_CPO_IMPL
// ============================================================================
 
#ifdef SEQAN3_DEPRECATED_310
#define SEQAN3_CPO_IMPL(PRIO, TERM)                                                                                  \
                                                                          \
template <typename t, typename ...arg_ts>                                                                            \
static constexpr decltype(auto) impl(seqan3::detail::priority_tag<PRIO>,                                             \
                                     [[maybe_unused]] t && v,                                                        \
                                     [[maybe_unused]] arg_ts && ... args)                                            \
    noexcept(noexcept(TERM))                                                                                         \
    requires requires (seqan3::detail::priority_tag<PRIO> const &/*<- need for doxygen*/, t && v, arg_ts && ... args)\
    { { TERM }; }                                                                                                    \
{                                                                                                                    \
    return TERM;                                                                                                     \
}
#endif // SEQAN3_DEPRECATED_310
 
#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