[range.transform] (original) (raw)

25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.9 Transform view [range.transform]

25.7.9.1 Overview [range.transform.overview]

25.7.9.2 Class template transform_view [range.transform.view]

25.7.9.3 Class template transform_view​::​iterator [range.transform.iterator]

25.7.9.4 Class template transform_view​::​sentinel [range.transform.sentinel]

25.7.9.1 Overview [range.transform.overview]

transform_view presents a view of an underlying sequence after applying a transformation function to each element.

Given subexpressions E and F, the expressionviews​::​transform(E, F) is expression-equivalent totransform_view(E, F).

[Example 1: vector<int> is{ 0, 1, 2, 3, 4 };auto squares = views::transform(is, [](int i) { return i * i; });for (int i : squares) cout << i << ' '; — _end example_]

25.7.9.2 Class template transform_view [range.transform.view]

namespace std::ranges { template<input_range V, move_constructible F> requires view<V> && is_object_v<F> && regular_invocable<F&, range_reference_t<V>> && can-reference<invoke_result_t<F&, range_reference_t<V>>> class transform_view : public view_interface<transform_view<V, F>> { private: template<bool> struct iterator; template<bool> struct sentinel; V base_ = V(); movable-box<F> fun_; public: transform_view() requires default_initializable<V> && default_initializable<F> = default;constexpr explicit transform_view(V base, F fun);constexpr V base() const & requires copy_constructible<V> { return base_; } constexpr V base() && { return std::move(base_); } constexpr iterator<false> begin();constexpr iterator<true> begin() const requires range<const V> && regular_invocable<const F&, range_reference_t<const V>>;constexpr sentinel<false> end();constexpr iterator<false> end() requires common_range<V>;constexpr sentinel<true> end() const requires range<const V> && regular_invocable<const F&, range_reference_t<const V>>;constexpr iterator<true> end() const requires common_range<const V> && regular_invocable<const F&, range_reference_t<const V>>;constexpr auto size() requires sized_range<V> { return ranges::size(base_); } constexpr auto size() const requires sized_range<const V> { return ranges::size(base_); } constexpr auto reserve_hint() requires approximately_sized_range<V> { return ranges::reserve_hint(base_); } constexpr auto reserve_hint() const requires approximately_sized_range<const V> { return ranges::reserve_hint(base_); } };template<class R, class F> transform_view(R&&, F) -> transform_view<views::all_t<R>, F>;}

constexpr explicit transform_view(V base, F fun);

Effects: Initializes base_ with std​::​move(base) and_fun__ with std​::​move(fun).

constexpr _iterator_<false> begin();

Effects: Equivalent to:return iterator<false>{*this, ranges::begin(base_)};

constexpr _iterator_<true> begin() const requires [range](range.range#concept:range "25.4.2 Ranges [range.range]")<const V> && [regular_invocable](concept.regularinvocable#concept:regular%5Finvocable "18.7.3 Concept regular_­invocable [concept.regularinvocable]")<const F&, range_reference_t<const V>>;

Effects: Equivalent to:return iterator<true>{*this, ranges::begin(base_)};

constexpr _sentinel_<false> end();

Effects: Equivalent to:return sentinel<false>{ranges::end(base_)};

Effects: Equivalent to:return iterator<false>{*this, ranges::end(base_)};

constexpr _sentinel_<true> end() const requires [range](range.range#concept:range "25.4.2 Ranges [range.range]")<const V> && [regular_invocable](concept.regularinvocable#concept:regular%5Finvocable "18.7.3 Concept regular_­invocable [concept.regularinvocable]")<const F&, range_reference_t<const V>>;

Effects: Equivalent to:return sentinel<true>{ranges::end(base_)};

Effects: Equivalent to:return iterator<true>{*this, ranges::end(base_)};

25.7.9.3 Class template transform_view​::​iterator [range.transform.iterator]

namespace std::ranges { template<input_range V, move_constructible F> requires view<V> && is_object_v<F> && regular_invocable<F&, range_reference_t<V>> && can-reference<invoke_result_t<F&, range_reference_t<V>>> template<bool Const> class transform_view<V, F>::iterator { private: using Parent = maybe-const<Const, transform_view>; using Base = maybe-const<Const, V>; iterator_t<_Base_> current_ = iterator_t<_Base_>(); Parent* parent_ = nullptr; public: using iterator_concept = see below;using iterator_category = see below; using value_type = remove_cvref_t<invoke_result_t<_maybe-const_<Const, F>&, range_reference_t<_Base_>>>;using difference_type = range_difference_t<_Base_>;iterator() requires default_initializable<iterator_t<_Base_>> = default;constexpr iterator(Parent& parent, iterator_t<_Base_> current);constexpr iterator(iterator<!Const> i) requires Const && convertible_to<iterator_t<V>, iterator_t<_Base_>>;constexpr const iterator_t<_Base_>& base() const & noexcept;constexpr iterator_t<_Base_> base() &&;constexpr decltype(auto) operator*() const noexcept(noexcept(invoke(*_parent__->fun_, *current_))) { return invoke(*_parent__->fun_, *current_);} 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 n) requires random_access_range<_Base_>;constexpr iterator& operator-=(difference_type n) requires random_access_range<_Base_>;constexpr decltype(auto) operator[](difference_type n) const requires random_access_range<_Base_> { return invoke(*_parent__->fun_, _current__[n]);} friend constexpr bool operator==(const iterator& x, const iterator& y) requires equality_comparable<iterator_t<_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 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<iterator_t<_Base_>>;friend constexpr iterator operator+(iterator i, difference_type n) requires random_access_range<_Base_>;friend constexpr iterator operator+(difference_type n, iterator i) requires random_access_range<_Base_>;friend constexpr iterator operator-(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<iterator_t<_Base_>, iterator_t<_Base_>>;};}

_iterator_​::​iterator_concept is defined as follows:

• Otherwise, if Base models bidirectional_range, theniterator_concept denotes bidirectional_iterator_tag.
• Otherwise, if Base models forward_range, theniterator_concept denotes forward_iterator_tag.
• Otherwise, iterator_concept denotes input_iterator_tag.

In that case,_iterator_​::​iterator_category is defined as follows: Let C denote the typeiterator_traits<iterator_t<_Base_>>​::​iterator_category.

• If is_reference_v<invoke_result_t<_maybe-const_<Const, F>&, range_reference_t<_Base_>>>is true, then
  • if C models derived_from<contiguous_iterator_tag>,iterator_category denotes random_access_iterator_tag;
  • otherwise,iterator_category denotes C.
• Otherwise, iterator_category denotes input_iterator_tag.

constexpr _iterator_(_Parent_& parent, iterator_t<_Base_> current);

Effects: Initializes current_ with std​::​move(current) and_parent__ with addressof(parent).

constexpr _iterator_(_iterator_<!Const> i) requires Const && [convertible_to](concept.convertible#concept:convertible%5Fto "18.4.4 Concept convertible_­to [concept.convertible]")<iterator_t<V>, iterator_t<_Base_>>;

Effects: Initializes current_ with std​::​move(i.current_) and_parent__ with i.parent_.

constexpr const iterator_t<_Base_>& base() const & noexcept;

Effects: Equivalent to: return current_;

constexpr iterator_t<_Base_> base() &&;

Effects: Equivalent to: return std​::​move(current_);

constexpr _iterator_& operator++();

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

constexpr void operator++(int);

Effects: Equivalent to ++current_.

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

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

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

Effects: Equivalent to:current_ += n;return *this;

Effects: Equivalent to:current_ -= n;return *this;

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]")<iterator_t<_Base_>>;

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

friend constexpr bool operator<(const _iterator_& x, const _iterator_& y) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.6 Other range refinements [range.refinements]")<_Base_>;

Effects: Equivalent to: return x.current_ < y.current_;

friend constexpr bool operator>(const _iterator_& x, const _iterator_& y) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.6 Other range refinements [range.refinements]")<_Base_>;

Effects: Equivalent to: return y < x;

friend constexpr bool operator<=(const _iterator_& x, const _iterator_& y) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.6 Other range refinements [range.refinements]")<_Base_>;

Effects: Equivalent to: return !(y < x);

friend constexpr bool operator>=(const _iterator_& x, const _iterator_& y) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.6 Other range refinements [range.refinements]")<_Base_>;

Effects: Equivalent to: return !(x < y);

Effects: Equivalent to: return x.current_ <=> y.current_;

friend constexpr _iterator_ operator+(_iterator_ i, difference_type n) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.6 Other range refinements [range.refinements]")<_Base_>;friend constexpr _iterator_ operator+(difference_type n, _iterator_ i) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.6 Other range refinements [range.refinements]")<_Base_>;

Effects: Equivalent to: return iterator{*i.parent_, i.current_ + n};

friend constexpr _iterator_ operator-(_iterator_ i, difference_type n) requires [random_access_range](range.refinements#concept:random%5Faccess%5Frange "25.4.6 Other range refinements [range.refinements]")<_Base_>;

Effects: Equivalent to: return iterator{*i.parent_, i.current_ - 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]")<iterator_t<_Base_>, iterator_t<_Base_>>;

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

25.7.9.4 Class template transform_view​::​sentinel [range.transform.sentinel]

namespace std::ranges { template<input_range V, move_constructible F> requires view<V> && is_object_v<F> && regular_invocable<F&, range_reference_t<V>> && can-reference<invoke_result_t<F&, range_reference_t<V>>> template<bool Const> class transform_view<V, F>::sentinel { private: using Parent = maybe-const<Const, transform_view>; using Base = maybe-const<Const, V>; sentinel_t<_Base_> end_ = sentinel_t<_Base_>(); public: sentinel() = default;constexpr explicit sentinel(sentinel_t<_Base_> end);constexpr sentinel(sentinel<!Const> i) requires Const && convertible_to<sentinel_t<V>, sentinel_t<_Base_>>;constexpr sentinel_t<_Base_> base() const;template<bool OtherConst> requires sentinel_for<sentinel_t<_Base_>, iterator_t<_maybe-const_<OtherConst, V>>> friend constexpr bool operator==(const iterator<OtherConst>& x, const sentinel& y);template<bool OtherConst> requires sized_sentinel_for<sentinel_t<_Base_>, iterator_t<_maybe-const_<OtherConst, V>>> friend constexpr range_difference_t<_maybe-const_<OtherConst, V>> operator-(const iterator<OtherConst>& x, const sentinel& y);template<bool OtherConst> requires sized_sentinel_for<sentinel_t<_Base_>, iterator_t<_maybe-const_<OtherConst, V>>> friend constexpr range_difference_t<_maybe-const_<OtherConst, V>> operator-(const sentinel& y, const iterator<OtherConst>& x);};}

constexpr explicit _sentinel_(sentinel_t<_Base_> end);

Effects: Initializes end_ with end.

constexpr _sentinel_(_sentinel_<!Const> i) requires Const && [convertible_to](concept.convertible#concept:convertible%5Fto "18.4.4 Concept convertible_­to [concept.convertible]")<sentinel_t<V>, sentinel_t<_Base_>>;

Effects: Initializes end_ with std​::​move(i.end_).

constexpr sentinel_t<_Base_> base() const;

Effects: Equivalent to: return end_;

template<bool OtherConst> requires [sentinel_for](iterator.concept.sentinel#concept:sentinel%5Ffor "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<sentinel_t<_Base_>, iterator_t<_maybe-const_<OtherConst, V>>> friend constexpr bool operator==(const _iterator_<OtherConst>& x, const _sentinel_& y);

Effects: Equivalent to: return x.current_ == y.end_;

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]")<sentinel_t<_Base_>, iterator_t<_maybe-const_<OtherConst, V>>> friend constexpr range_difference_t<_maybe-const_<OtherConst, V>> operator-(const _iterator_<OtherConst>& x, const _sentinel_& y);

Effects: Equivalent to: return x.current_ - y.end_;

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]")<sentinel_t<_Base_>, iterator_t<_maybe-const_<OtherConst, V>>> friend constexpr range_difference_t<_maybe-const_<OtherConst, V>> operator-(const _sentinel_& y, const _iterator_<OtherConst>& x);

Effects: Equivalent to: return y.end_ - x.current_;