namespace std::ranges {
template<class R>
concept bidirectional-common = bidirectional_range<R> && common_range<R>;
template<input_range V, forward_range Pattern>
requires view<V> && input_range<range_reference_t<V>>
&& view<Pattern>
&& concatable<range_reference_t<V>, Pattern>
class join_with_view : public view_interface<join_with_view<V, Pattern>> {
using InnerRng = range_reference_t<V>;
V base_ = V();
non-propagating-cache<iterator_t<V>> outer_it_;
non-propagating-cache<remove_cv_t<InnerRng>> inner_;
Pattern pattern_ = Pattern();
template<bool Const> struct iterator;
template<bool Const> struct sentinel;
public:
join_with_view()
requires default_initializable<V> && default_initializable<Pattern> = default;
constexpr explicit join_with_view(V base, Pattern pattern);
template<input_range R>
requires constructible_from<V, views::all_t<R>> &&
constructible_from<Pattern, single_view<range_value_t<InnerRng>>>
constexpr explicit join_with_view(R&& r, range_value_t<InnerRng> e);
constexpr V base() const & requires copy_constructible<V> { return base_; }
constexpr V base() && { return std::move(base_); }
constexpr auto begin() {
if constexpr (forward_range<V>) {
constexpr bool use_const =
simple-view<V> && is_reference_v<InnerRng> && simple-view<Pattern>;
return iterator<use_const>{*this, ranges::begin(base_)};
}
else {
outer_it_ = ranges::begin(base_);
return iterator<false>{*this};
}
}
constexpr auto begin() const
requires forward_range<const V> &&
forward_range<const Pattern> &&
is_reference_v<range_reference_t<const V>> &&
input_range<range_reference_t<const V>> &&
concatable<range_reference_t<const V>, const Pattern> {
return iterator<true>{*this, ranges::begin(base_)};
}
constexpr auto end() {
if constexpr (forward_range<V> &&
is_reference_v<InnerRng> && forward_range<InnerRng> &&
common_range<V> && common_range<InnerRng>)
return iterator<simple-view<V> && simple-view<Pattern>>{*this, ranges::end(base_)};
else
return sentinel<simple-view<V> && simple-view<Pattern>>{*this};
}
constexpr auto end() const
requires forward_range<const V> && forward_range<const Pattern> &&
is_reference_v<range_reference_t<const V>> &&
input_range<range_reference_t<const V>> &&
concatable<range_reference_t<const V>, const Pattern> {
using InnerConstRng = range_reference_t<const V>;
if constexpr (forward_range<InnerConstRng> &&
common_range<const V> && common_range<InnerConstRng>)
return iterator<true>{*this, ranges::end(base_)};
else
return sentinel<true>{*this};
}
};
template<class R, class P>
join_with_view(R&&, P&&) -> join_with_view<views::all_t<R>, views::all_t<P>>;
template<input_range R>
join_with_view(R&&, range_value_t<range_reference_t<R>>)
-> join_with_view<views::all_t<R>, single_view<range_value_t<range_reference_t<R>>>>;
}
constexpr explicit join_with_view(V base, Pattern pattern);
Effects: Initializes
base_ with
std::move(base) and
pattern_ with
std::move(pattern). Effects: Initializes
base_ with
views::all(std::forward<R>(r)) and
pattern_ with
views::single(std::move(e)).