[range.adjacent.transform] (original) (raw)

25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.28 Adjacent transform view [range.adjacent.transform]

25.7.28.1 Overview [range.adjacent.transform.overview]

adjacent_transform_view takes an invocable object and a view and produces a view whose element is the result of applying the invocable object to the through elements of the original view.

If the original view has fewer than N elements, the resulting view is empty.

The name views::adjacent_transform<N> denotes a range adaptor object ([range.adaptor.object]).

Given subexpressions E and F and a constant expression N:

If N is equal to 0 anddecltype((E)) models forward_range,views::adjacent_transform<N>(E, F) is expression-equivalent to((void)E, views::zip_transform(F)), except that the evaluations of E and F are indeterminately sequenced.
Otherwise, the expression views::adjacent_transform<N>(E, F) is expression-equivalent toadjacent_transform_view<views::all_t<decltype((E))>, decay_t<decltype((F))>, N>(E, F).

[Example 1: vector v = {1, 2, 3, 4};for (auto i : v | views::adjacent_transform<2>(std::multiplies())) { cout << i << ' '; } — _end example_]

25.7.28.2 Class template adjacent_transform_view [range.adjacent.transform.view]

namespace std::ranges { template<forward_range V, move_constructible F, size_t N> requires view<V> && (N > 0) && is_object_v<F> && regular_invocable<F&, _REPEAT_(range_reference_t<V>, N)...> && can-reference<invoke_result_t<F&, _REPEAT_(range_reference_t<V>, N)...>> class adjacent_transform_view : public view_interface<adjacent_transform_view<V, F, N>> { movable-box<F> fun_; adjacent_view<V, N> inner_; using InnerView = adjacent_view<V, N>; template<bool Const> using inner-iterator = iterator_t<_maybe-const_<Const, _InnerView_>>; template<bool Const> using inner-sentinel = sentinel_t<_maybe-const_<Const, _InnerView_>>; template<bool> class iterator; template<bool> class sentinel; public: adjacent_transform_view() = default;constexpr explicit adjacent_transform_view(V base, F fun);constexpr V base() const & requires copy_constructible<V> { return inner_.base(); } constexpr V base() && { return std::move(inner_).base(); } constexpr auto begin() { return iterator<false>(*this, inner_.begin());} constexpr auto begin() const requires range<const _InnerView_> && regular_invocable<const F&, _REPEAT_(range_reference_t<const V>, N)...> { return iterator<true>(*this, inner_.begin());} constexpr auto end() { if constexpr (common_range<_InnerView_>) { return iterator<false>(*this, inner_.end());} else { return sentinel<false>(inner_.end());} } constexpr auto end() const requires range<const _InnerView_> && regular_invocable<const F&, _REPEAT_(range_reference_t<const V>, N)...> { if constexpr (common_range<const _InnerView_>) { return iterator<true>(*this, inner_.end());} else { return sentinel<true>(inner_.end());} } constexpr auto size() requires sized_range<_InnerView_> { return inner_.size();} constexpr auto size() const requires sized_range<const _InnerView_> { return inner_.size();} constexpr auto reserve_hint() requires approximately_sized_range<_InnerView_> { return inner_.reserve_hint();} constexpr auto reserve_hint() const requires approximately_sized_range<const _InnerView_> { return inner_.reserve_hint();} };}

constexpr explicit adjacent_transform_view(V base, F fun);

Effects: Initializes fun_ with std::move(fun) and_inner__ with std::move(base).

25.7.28.3 Class template adjacent_transform_view::iterator [range.adjacent.transform.iterator]

namespace std::ranges { template<forward_range V, move_constructible F, size_t N> requires view<V> && (N > 0) && is_object_v<F> && regular_invocable<F&, _REPEAT_(range_reference_t<V>, N)...> && can-reference<invoke_result_t<F&, _REPEAT_(range_reference_t<V>, N)...>> template<bool Const> class adjacent_transform_view<V, F, N>::iterator { using Parent = maybe-const<Const, adjacent_transform_view>; using Base = maybe-const<Const, V>; Parent* parent_ = nullptr; inner-iterator<Const> inner_; constexpr iterator(Parent& parent, inner-iterator<Const> inner); public: using iterator_category = see below;using iterator_concept = typename inner-iterator<Const>::iterator_concept;using value_type = remove_cvref_t<invoke_result_t<_maybe-const_<Const, F>&,REPEAT(range_reference_t<_Base_>, N)...>>;using difference_type = range_difference_t<_Base_>;iterator() = default;constexpr iterator(iterator<!Const> i) requires Const && convertible_to<_inner-iterator_<false>, inner-iterator<Const>>;constexpr decltype(auto) operator*() const noexcept(see below);constexpr iterator& operator++();constexpr iterator operator++(int);constexpr iterator& operator--() requires bidirectional_range<_Base_>;constexpr iterator operator--(int) requires bidirectional_range<_Base_>;constexpr iterator& operator+=(difference_type x) requires random_access_range<_Base_>;constexpr iterator& operator-=(difference_type x) requires random_access_range<_Base_>;constexpr decltype(auto) operator[](difference_type n) const requires random_access_range<_Base_>;friend constexpr bool operator==(const iterator& x, const iterator& y);friend constexpr bool operator<(const _iterator_& x, const _iterator_& y) requires random_access_range<_Base_>;friend constexpr bool operator>(const iterator& x, const iterator& y) requires random_access_range<_Base_>;friend constexpr bool operator<=(const _iterator_& x, const _iterator_& y) requires random_access_range<_Base_>;friend constexpr bool operator>=(const iterator& x, const iterator& y) requires random_access_range<_Base_>;friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires random_access_range<_Base_> && three_way_comparable<_inner-iterator_<Const>>;friend constexpr iterator operator+(const iterator& i, difference_type n) requires random_access_range<_Base_>;friend constexpr iterator operator+(difference_type n, const iterator& i) requires random_access_range<_Base_>;friend constexpr iterator operator-(const iterator& i, difference_type n) requires random_access_range<_Base_>;friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires sized_sentinel_for<_inner-iterator_<Const>, inner-iterator<Const>>;};}

The member typedef-name _iterator_::iterator_categoryis defined as follows:

If invoke_result_t<_maybe-const_<Const, F>&,REPEAT(range_reference_t<_Base_>, N)...>is not a reference,iterator_category denotes input_iterator_tag.
Otherwise, let C denote the typeiterator_traits<iterator_t<_Base_>>::iterator_category.
- If derived_from<C, random_access_iterator_tag>is true,iterator_category denotes random_access_iterator_tag.
- Otherwise, if derived_from<C, bidirectional_iterator_tag>is true,iterator_category denotes bidirectional_iterator_tag.
- Otherwise, if derived_from<C, forward_iterator_tag>is true,iterator_category denotes forward_iterator_tag.
- Otherwise, iterator_category denotes input_iterator_tag.

constexpr _iterator_(_Parent_& parent, _inner-iterator_<Const> inner);

Effects: Initializes parent_ with addressof(parent) and_inner__ with std::move(inner).

constexpr _iterator_(_iterator_<!Const> i) requires Const && [convertible_to](concept.convertible#concept:convertible%5Fto "18.4.4 Concept convertible_to [concept.convertible]")<_inner-iterator_<false>, _inner-iterator_<Const>>;

Effects: Initializes parent_ with i.parent_ and_inner__ with std::move(i.inner_).

constexpr decltype(auto) operator*() const noexcept(_see below_);

Effects: Equivalent to:return apply([&](const auto&... iters) -> decltype(auto) { return invoke(*_parent__->fun_, *iters...);}, inner_.current_);

Remarks: Let Is be the pack 0, 1, …, (N - 1).

The exception specification is equivalent to:noexcept(invoke(*_parent__->fun_, *std::get<Is>(inner_.current_)...))

constexpr _iterator_& operator++();

Effects: Equivalent to:++inner_;return *this;

constexpr _iterator_ operator++(int);

Effects: Equivalent to:auto tmp = *this;++*this;return tmp;

Effects: Equivalent to:--inner_;return *this;

Effects: Equivalent to:auto tmp = *this;--*this;return tmp;

Effects: Equivalent to:inner_ += x;return *this;

Effects: Equivalent to:inner_ -= x;return *this;

constexpr decltype(auto) operator[](difference_type n) const requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.5 Other range refinements [range.refinements]")<_Base_>;

Effects: Equivalent to:return apply([&](const auto&... iters) -> decltype(auto) { return invoke(*_parent__->fun_, iters[n]...);}, inner_.current_);

friend constexpr bool operator==(const _iterator_& x, const _iterator_& y);friend constexpr bool operator<(const _iterator_& x, const _iterator_& y) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.5 Other range refinements [range.refinements]")<_Base_>;friend constexpr bool operator>(const _iterator_& x, const _iterator_& y) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.5 Other range refinements [range.refinements]")<_Base_>;friend constexpr bool operator<=(const _iterator_& x, const _iterator_& y) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.5 Other range refinements [range.refinements]")<_Base_>;friend constexpr bool operator>=(const _iterator_& x, const _iterator_& y) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.5 Other range refinements [range.refinements]")<_Base_>;friend constexpr auto operator<=>(const _iterator_& x, const _iterator_& y) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.5 Other range refinements [range.refinements]")<_Base_> && [three_way_comparable](cmp.concept#concept:three%5Fway%5Fcomparable "17.12.4 Concept three_way_comparable [cmp.concept]")<_inner-iterator_<Const>>;

Effects: Equivalent to: return x.inner_ op y.inner_;

friend constexpr _iterator_ operator+(const _iterator_& i, difference_type n) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.5 Other range refinements [range.refinements]")<_Base_>;friend constexpr _iterator_ operator+(difference_type n, const _iterator_& i) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.5 Other range refinements [range.refinements]")<_Base_>;

Effects: Equivalent to: return iterator(*i.parent_, i.inner_ + n);

friend constexpr _iterator_ operator-(const _iterator_& i, difference_type n) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.5 Other range refinements [range.refinements]")<_Base_>;

Effects: Equivalent to: return iterator(*i.parent_, i.inner_ - n);

friend constexpr difference_type operator-(const _iterator_& x, const _iterator_& y) requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized%5Fsentinel%5Ffor "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<_inner-iterator_<Const>, _inner-iterator_<Const>>;

Effects: Equivalent to: return x.inner_ - y.inner_;

25.7.28.4 Class template adjacent_transform_view::sentinel [range.adjacent.transform.sentinel]

constexpr explicit _sentinel_(_inner-sentinel_<Const> inner);

Effects: Initializes inner_ with inner.

constexpr _sentinel_(_sentinel_<!Const> i) requires Const && [convertible_to](concept.convertible#concept:convertible%5Fto "18.4.4 Concept convertible_to [concept.convertible]")<_inner-sentinel_<false>, _inner-sentinel_<Const>>;

Effects: Initializes inner_ with std::move(i.inner_).

template<bool OtherConst> requires [sentinel_for](iterator.concept.sentinel#concept:sentinel%5Ffor "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<_inner-sentinel_<Const>, _inner-iterator_<OtherConst>> friend constexpr bool operator==(const _iterator_<OtherConst>& x, const _sentinel_& y);

Effects: Equivalent to: return x.inner_ == y.inner_;

template<bool OtherConst> requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized%5Fsentinel%5Ffor "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<_inner-sentinel_<Const>, _inner-iterator_<OtherConst>> friend constexpr range_difference_t<_maybe-const_<OtherConst, _InnerView_>> operator-(const _iterator_<OtherConst>& x, const _sentinel_& y);template<bool OtherConst> requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized%5Fsentinel%5Ffor "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<_inner-sentinel_<Const>, _inner-iterator_<OtherConst>> friend constexpr range_difference_t<_maybe-const_<OtherConst, _InnerView_>> operator-(const _sentinel_& x, const _iterator_<OtherConst>& y);