C++23Backports.hpp

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//          Copyright Dominic (DNKpp) Koepke 2024-2026.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          https://www.boost.org/LICENSE_1_0.txt)
 
#ifndef MIMICPP_PRINTING_STATE_CXX23_BACKPORTS_HPP
#define MIMICPP_PRINTING_STATE_CXX23_BACKPORTS_HPP
 
#pragma once
 
#include "mimic++/config/Config.hpp"
#include "mimic++/printing/Format.hpp"
#include "mimic++/printing/state/Print.hpp"
 
#ifndef MIMICPP_DETAIL_IS_MODULE
    #include <concepts>
    #include <functional>
    #include <ranges>
    #include <tuple>
    #include <utility>
#endif
 
namespace mimicpp::printing::detail::state
{
    template <std::ranges::forward_range Range>
    struct cxx23_backport_printer<Range>
    {
        template <print_iterator OutIter>
        static constexpr OutIter print(OutIter out, auto& range)
        {
            out = format::format_to(std::move(out), "[");
            auto iter = std::ranges::begin(range);
            if (const auto end = std::ranges::end(range);
                iter != end)
            {
                out = mimicpp::print(std::move(out), *iter++);
 
                for (; iter != end; ++iter)
                {
                    out = format::format_to(std::move(out), ", ");
                    out = mimicpp::print(std::move(out), *iter);
                }
            }
 
            return format::format_to(std::move(out), "]");
        }
    };
 
    template <std::size_t index, print_iterator OutIter>
    constexpr OutIter print_tuple_element(OutIter out, auto& tuple)
    {
        if constexpr (0u != index)
        {
            out = format::format_to(std::move(out), ", ");
        }
 
        using std::get;
        return mimicpp::print(std::move(out), get<index>(tuple));
    }
 
    template <typename Tuple, typename IndexSequence>
    struct has_tuple_element;
 
    // clang-format off
    template <typename Tuple, std::size_t index>
    struct has_tuple_element<Tuple, std::index_sequence<index>>
        : std::bool_constant<requires {typename std::tuple_element_t<index, Tuple>; }>
    {
    };
 
    // clang-format on
 
    template <typename Tuple, std::size_t... indices>
    struct has_tuple_element<Tuple, std::index_sequence<indices...>>
        : std::conjunction<
              has_tuple_element<Tuple, std::index_sequence<indices>>...>
    {
    };
 
    template <typename T>
    concept tuple_like = requires {
        typename std::tuple_size<T>::type;
        { std::tuple_size_v<T> } -> std::convertible_to<std::size_t>;
        requires 0u <= std::tuple_size_v<T>;
        requires has_tuple_element<T, std::make_index_sequence<std::tuple_size_v<T>>>::value;
    };
 
    template <tuple_like T>
    struct cxx23_backport_printer<T>
    {
        template <print_iterator OutIter>
        static constexpr OutIter print(OutIter out, auto& tuple)
        {
            out = format::format_to(std::move(out), "(");
            std::invoke(
                [&]<std::size_t... indices>(std::index_sequence<indices...> const /*sequence*/) {
                    (...,
                     (out = state::print_tuple_element<indices>(std::move(out), tuple)));
                },
                std::make_index_sequence<std::tuple_size_v<T>>{});
 
            return format::format_to(std::move(out), ")");
        }
    };
}
 
#endif