concepts.hpp

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// Range v3 library
//
//  Copyright Eric Niebler 2013-present
//
//  Use, modification and distribution is subject to the
//  Boost Software License, Version 1.0. (See accompanying
//  file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)
//
// Project home: https://github.com/ericniebler/range-v3
//
 
#ifndef RANGES_V3_ACTION_CONCEPTS_HPP
#define RANGES_V3_ACTION_CONCEPTS_HPP
 
#include <utility>
 
#include <meta/meta.hpp>
 
#include <range/v3/range_fwd.hpp>
 
#include <range/v3/range/concepts.hpp>
#include <range/v3/range/traits.hpp>
 
#include <range/v3/detail/prologue.hpp>
 
namespace ranges
{
    namespace detail
    {
        template<typename T>
        struct movable_input_iterator
        {
            using iterator_category = std::input_iterator_tag;
            using value_type = T;
            using difference_type = std::ptrdiff_t;
            using pointer = T *;
            using reference = T &&;
 
            movable_input_iterator() = default;
            movable_input_iterator & operator++();
            movable_input_iterator operator++(int);
            bool operator==(movable_input_iterator const &) const;
            bool operator!=(movable_input_iterator const &) const;
            T && operator*() const;
        };
    } // namespace detail

 
    // clang-format off
    template<typename T>
    CPP_concept semi_container =
        forward_range<T> && default_constructible<uncvref_t<T>> &&
        movable<uncvref_t<T>> &&
        !view_<T>;

    template(typename T)(
    concept (container_)(T),
        constructible_from<
            uncvref_t<T>,
            detail::movable_input_iterator<range_value_t<T>>,
            detail::movable_input_iterator<range_value_t<T>>>
    );

    template<typename T>
    CPP_concept container =
        semi_container<T> &&
        CPP_concept_ref(ranges::container_, T);

    template<typename C>
    CPP_requires(reservable_,
        requires(C & c, C const & cc) //
        (
            c.reserve(ranges::size(c)),
            cc.capacity(),
            cc.max_size(),
            concepts::requires_<same_as<decltype(cc.capacity()),
                                        decltype(ranges::size(c))>>,
            concepts::requires_<same_as<decltype(cc.max_size()),
                                        decltype(ranges::size(c))>>
        ));

    template<typename C>
    CPP_concept reservable =
        container<C> && sized_range<C> && CPP_requires_ref(ranges::reservable_, C);

    template<typename C, typename I>
    CPP_requires(reservable_with_assign_,
        requires(C & c, I i) //
        (
            c.assign(i, i)
        ));
    template<typename C, typename I>
    CPP_concept reservable_with_assign =
        reservable<C> && //
        input_iterator<I> && //
        CPP_requires_ref(ranges::reservable_with_assign_, C, I);

    template<typename C>
    CPP_concept random_access_reservable =
        reservable<C> && random_access_range<C>;
    // clang-format on

    namespace detail
    {
        template(typename T)(
            requires container<T>)
        std::true_type is_lvalue_container_like(T &) noexcept
        {
            return {};
        }
 
        template(typename T)(
            requires container<T>)
        meta::not_<std::is_rvalue_reference<T>> //
        is_lvalue_container_like(reference_wrapper<T>) noexcept
        {
            return {};
        }
 
        template(typename T)(
            requires container<T>)
        std::true_type is_lvalue_container_like(std::reference_wrapper<T>) noexcept
        {
            return {};
        }
 
        template(typename T)(
            requires container<T>)
        std::true_type is_lvalue_container_like(ref_view<T>) noexcept
        {
            return {};
        }
 
        template<typename T>
        using is_lvalue_container_like_t =
            decltype(detail::is_lvalue_container_like(std::declval<T>()));
 
    } // namespace detail
 
    // clang-format off
    template(typename T)(
    concept (lvalue_container_like_)(T),
        implicitly_convertible_to<detail::is_lvalue_container_like_t<T>, std::true_type>
    );
    template<typename T>
    CPP_concept lvalue_container_like =
        forward_range<T> &&
        CPP_concept_ref(ranges::lvalue_container_like_, T);
    // clang-format on
} // namespace ranges
 
#include <range/v3/detail/epilogue.hpp>
 
#endif