begin.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2023 Tobias Hienzsch
 
#ifndef TETL_RANGES_BEGIN_HPP
#define TETL_RANGES_BEGIN_HPP
 
#include <etl/_iterator/input_or_output_iterator.hpp>
#include <etl/_ranges/can_borrow.hpp>
#include <etl/_ranges/decay_copy.hpp>
 
namespace etl::ranges {
 
namespace begin_cpo {
 
auto begin(auto&) -> void       = delete;
auto begin(auto const&) -> void = delete;
 
template <typename T>
concept has_member_begin = ranges::detail::can_borrow<T> and requires(T&& t) {
    { decay_copy(t.begin()) } -> input_or_output_iterator;
};
 
template <typename T>
concept has_adl_begin = not has_member_begin<T> and ranges::detail::can_borrow<T> and requires(T&& t) {
    { decay_copy(begin(t)) } -> input_or_output_iterator;
};
 
struct fn {
    template <typename T>
        requires(sizeof(T) >= 0) // NOLINT(bugprone-sizeof-expression)
    [[nodiscard]] constexpr auto operator()(T (&t)[]) const noexcept
    {
        return t + 0;
    }
 
    template <typename T, etl::size_t Size>
        requires(sizeof(T) >= 0) // NOLINT(bugprone-sizeof-expression)
    [[nodiscard]] constexpr auto operator()(T (&t)[Size]) const noexcept
    {
        return t + 0;
    }
 
    template <has_member_begin T>
    [[nodiscard]] constexpr auto operator()(T&& t) const noexcept(noexcept(decay_copy(t.begin())))
    {
        return decay_copy(t.begin());
    }
 
    template <has_adl_begin T>
    [[nodiscard]] constexpr auto operator()(T&& t) const noexcept(noexcept(decay_copy(begin(t))))
    {
        return decay_copy(begin(t));
    }
 
    auto operator()(auto&&) const -> void = delete;
};
 
} // namespace begin_cpo
 
inline namespace cpo {
/// \ingroup ranges
inline constexpr auto begin = begin_cpo::fn{};
} // namespace cpo
 
} // namespace etl::ranges
 
#endif // TETL_RANGES_BEGIN_HPP