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

25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.26 Zip transform view [range.zip.transform]

25.7.26.1 Overview [range.zip.transform.overview]

zip_transform_view takes an invocable object and any number of views and produces a view whose element is the result of applying the invocable object to the elements of all views.

Let F be a subexpression, and let Es... be a pack of subexpressions.

• If Es is an empty pack, let FD be decay_t<decltype((F))>.
  • If move_constructible<FD> && regular_invocable<FD&> is false, or if decay_t<invoke_result_t<FD&>> is not an object type,views​::​zip_transform(F, Es...) is ill-formed.
  • Otherwise, the expression views​::​zip_transform(F, Es...)is expression-equivalent to((void)F, auto(views::empty<decay_t<invoke_result_t<FD&>>>))
• Otherwise, the expression views​::​zip_transform(F, Es...)is expression-equivalent to zip_transform_view(F, Es...).

[Example 1: vector v1 = {1, 2}; vector v2 = {4, 5, 6};for (auto i : views::zip_transform(plus(), v1, v2)) { cout << i << ' '; } — _end example_]

25.7.26.2 Class template zip_transform_view [range.zip.transform.view]

namespace std::ranges { template<move_constructible F, input_range... Views> requires (view<Views> && ...) && (sizeof...(Views) > 0) && is_object_v<F> && regular_invocable<F&, range_reference_t<Views>...> && can-reference<invoke_result_t<F&, range_reference_t<Views>...>> class zip_transform_view : public view_interface<zip_transform_view<F, Views...>> { movable-box<F> fun_; zip_view<Views...> zip_; using InnerView = zip_view<Views...>; template<bool Const> using ziperator = iterator_t<_maybe-const_<Const, _InnerView_>>; template<bool Const> using zentinel = sentinel_t<_maybe-const_<Const, _InnerView_>>; template<bool> class iterator; template<bool> class sentinel; public: zip_transform_view() = default;constexpr explicit zip_transform_view(F fun, Views... views);constexpr auto begin() { return iterator<false>(*this, zip_.begin()); } constexpr auto begin() const requires range<const _InnerView_> && regular_invocable<const F&, range_reference_t<const Views>...> { return iterator<true>(*this, zip_.begin());} constexpr auto end() { if constexpr (common_range<_InnerView_>) { return iterator<false>(*this, zip_.end());} else { return sentinel<false>(zip_.end());} } constexpr auto end() const requires range<const _InnerView_> && regular_invocable<const F&, range_reference_t<const Views>...> { if constexpr (common_range<const _InnerView_>) { return iterator<true>(*this, zip_.end());} else { return sentinel<true>(zip_.end());} } constexpr auto size() requires sized_range<_InnerView_> { return zip_.size();} constexpr auto size() const requires sized_range<const _InnerView_> { return zip_.size();} };template<class F, class... Rs> zip_transform_view(F, Rs&&...) -> zip_transform_view<F, views::all_t<Rs>...>;}

constexpr explicit zip_transform_view(F fun, Views... views);

Effects: Initializes fun_ with std​::​move(fun) and_zip__ with std​::​move(views)....

25.7.26.3 Class template zip_transform_view​::​iterator [range.zip.transform.iterator]

namespace std::ranges { template<move_constructible F, input_range... Views> requires (view<Views> && ...) && (sizeof...(Views) > 0) && is_object_v<F> && regular_invocable<F&, range_reference_t<Views>...> && can-reference<invoke_result_t<F&, range_reference_t<Views>...>> template<bool Const> class zip_transform_view<F, Views...>::iterator { using Parent = maybe-const<Const, zip_transform_view>; using Base = maybe-const<Const, _InnerView_>; Parent* parent_ = nullptr; ziperator<Const> inner_; constexpr iterator(Parent& parent, ziperator<Const> inner); public: using iterator_category = see below; using iterator_concept = typename ziperator<Const>::iterator_concept;using value_type = remove_cvref_t<invoke_result_t<_maybe-const_<Const, F>&, range_reference_t<_maybe-const_<Const, Views>>...>>;using difference_type = range_difference_t<_Base_>;iterator() = default;constexpr iterator(iterator<!Const> i) requires Const && convertible_to<_ziperator_<false>, ziperator<Const>>;constexpr decltype(auto) operator*() const noexcept(see below);constexpr iterator& operator++();constexpr void operator++(int);constexpr iterator operator++(int) requires forward_range<_Base_>;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) requires equality_comparable<_ziperator_<Const>>;friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires random_access_range<_Base_>;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<_ziperator_<Const>, ziperator<Const>>;};}

The member typedef-name _iterator_​::​iterator_categoryis defined if and only if Base models forward_range.

In that case,_iterator_​::​iterator_category is defined as follows:

• Ifinvoke_result_t<_maybe-const_<Const, F>&, range_reference_t<_maybe-const_<Const, Views>>...> is not a reference,iterator_category denotes input_iterator_tag.
• Otherwise, let Cs denote the pack of typesiterator_traits<iterator_t<_maybe-const_<Const, Views>>>​::​iterator_category....
  • If (derived_from<Cs, random_access_iterator_tag> && ...)is true,iterator_category denotes random_access_iterator_tag.
  • Otherwise, if (derived_from<Cs, bidirectional_iterator_tag> && ...)is true,iterator_category denotes bidirectional_iterator_tag.
  • Otherwise, if (derived_from<Cs, forward_iterator_tag> && ...)is true,iterator_category denotes forward_iterator_tag.
  • Otherwise, iterator_category denotes input_iterator_tag.

constexpr _iterator_(_Parent_& parent, _ziperator_<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]")<_ziperator_<false>, _ziperator_<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, …, (sizeof...(Views) - 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 void operator++(int);

Effects: Equivalent to: ++*this.

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([&]<class... Is>(const Is&... iters) -> decltype(auto) { return invoke(*_parent__->fun_, iters[iter_difference_t<Is>(n)]...);}, inner_.current_);

friend constexpr bool operator==(const _iterator_& x, const _iterator_& y) requires [equality_comparable](concept.equalitycomparable#concept:equality%5Fcomparable "18.5.4 Concept equality_­comparable [concept.equalitycomparable]")<_ziperator_<Const>>;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_>;

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]")<_ziperator_<Const>, _ziperator_<Const>>;

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

25.7.26.4 Class template zip_transform_view​::​sentinel [range.zip.transform.sentinel]

namespace std::ranges { template<move_constructible F, input_range... Views> requires (view<Views> && ...) && (sizeof...(Views) > 0) && is_object_v<F> && regular_invocable<F&, range_reference_t<Views>...> && can-reference<invoke_result_t<F&, range_reference_t<Views>...>> template<bool Const> class zip_transform_view<F, Views...>::sentinel { zentinel<Const> inner_; constexpr explicit sentinel(zentinel<Const> inner); public: sentinel() = default;constexpr sentinel(sentinel<!Const> i) requires Const && convertible_to<_zentinel_<false>, zentinel<Const>>;template<bool OtherConst> requires sentinel_for<_zentinel_<Const>, ziperator<OtherConst>> friend constexpr bool operator==(const iterator<OtherConst>& x, const sentinel& y);template<bool OtherConst> requires sized_sentinel_for<_zentinel_<Const>, ziperator<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<_zentinel_<Const>, ziperator<OtherConst>> friend constexpr range_difference_t<_maybe-const_<OtherConst, _InnerView_>> operator-(const sentinel& x, const iterator<OtherConst>& y);};}

constexpr explicit _sentinel_(_zentinel_<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]")<_zentinel_<false>, _zentinel_<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]")<_zentinel_<Const>, _ziperator_<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]")<_zentinel_<Const>, _ziperator_<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]")<_zentinel_<Const>, _ziperator_<OtherConst>> friend constexpr range_difference_t<_maybe-const_<OtherConst, _InnerView_>> operator-(const _sentinel_& x, const _iterator_<OtherConst>& y);

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