std::ranges::iota_view<W, Bound>::iterator

 

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Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata reserve_hint (C++26)   empty

Range conversions std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

Dangling iterator handling dangling borrowed_iterator_t borrowed_subrange_t

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range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

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range borrowed_range    common_range	sized_range viewable_range    view	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	approximately_sized_range (C++26) constant_range (C++23)

Views
view_interface	subrange

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empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

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views::all_tviews::all as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while common_viewviews::common views::counted as_input_viewviews::as_input (C++26)(C++26)	ref_view drop_viewviews::drop drop_while_viewviews::drop_while lazy_split_viewviews::lazy_split split_viewviews::split join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   concat_viewviews::concat (C++26)(C++26) cache_latest_viewviews::cache_latest (C++26)(C++26)	owning_view reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)

Range generators std::generator (C++23)

Range adaptor closure objects range_adaptor_closure (C++23)

Range adaptor objects

Helper items
copyable-box movable-box (until C++23)  (C++23)	simple-view non-propagating-cache

 

std::ranges::iota_view

Member functions

iota_view::iota_view

iota_view::begin

iota_view::end

iota_view::empty

iota_view::size

Deduction guides

Nested classes

Iterator

Helper concepts

decrementable

advanceable

Member types

Member functions

iota_view::iterator::iterator

iota_view::iterator::operator*

iota_view::iterator::operator[]

iota_view::iterator::operator++ iota_view::iterator::operator++(int)

iota_view::iterator::operator-- iota_view::iterator::operator--(int)

iota_view::iterator::operator+=

iota_view::iterator::operator-=

Non-member functions

operator==(iota_view::iterator) operator<(iota_view::iterator) operator>(iota_view::iterator) operator<=(iota_view::iterator) operator>=(iota_view::iterator) operator<=>(iota_view::iterator)

operator+(iota_view::iterator)

operator-(iota_view::iterator)

Sentinel

Member functions

iota_view::sentinel::sentinel

Non-member functions

operator==(iota_view::iterator,iota_view::sentinel)

operator-(iota_view::iterator,iota_view::sentinel)

 

struct /*iterator*/;	(1)	(exposition only*)
Helper alias templates
template< class I > using /*iota-diff-t*/ = /* see below */;	(2)	(exposition only*)
Helper concepts
template< class I > concept /*decrementable*/ = std::incrementable<I> && requires(I i) { { --i } -> std::same_as<I&>; { i-- } -> std::same_as<I>; };	(3)	(exposition only*)
template< class I > concept /*advanceable*/ = /*decrementable*/<I> && std::totally_ordered<I> && requires(I i, const I j, const /*iota-diff-t*/<I> n) { { i += n } -> std::same_as<I&>; { i -= n } -> std::same_as<I&>; I(j + n); I(n + j); I(j - n); { j - j } -> std::convertible_to</*iota-diff-t*/<I>>; };	(4)	(exposition only*)

1) ranges::iota_view<W, Bound>::iterator is the type of the iterators returned by begin() and end() of ranges::iota_view<W, Bound>.

2) Calculates the difference type for both iterator types and integer-like types.

• If I is not an integral type, or if it is an integral type and sizeof(std::iter_difference_t<I>) is greater than sizeof(I), then /*iota-diff-t*/<I> is std::iter_difference_t<I>.
• Otherwise, /*iota-diff-t*/<I> is a signed integer type of width greater than the width of I if such a type exists.
• Otherwise, I is one of the widest integral types, and /*iota-diff-t*/<I> is an unspecified signed-integer-like type of width not less than the width of I. It is unspecified whether /*iota-diff-t*/<I> models weakly_incrementable in this case.

3) Specifies that a type is incrementable, and pre- and post- operator-- for the type have common meaning.

4) Specifies that a type is both decrementable and totally_ordered, and operator+=, operator-=, operator+, and operator- among the type and its different type have common meaning.

See More

/*iterator*/ models

• random_access_iterator if W models advanceable (4),
• bidirectional_iterator if W models decrementable (3),
• forward_iterator if W models incrementable, and
• input_iterator otherwise.

However, it only satisfies LegacyInputIterator if W models incrementable, and does not satisfy LegacyInputIterator otherwise.

Semantic requirements

3) Type I models decrementable only if I satisfies decrementable and all concepts it subsumes are modeled, and given equal objects a and b of type I:

• If a and b are in the domain of both pre- and post- operator-- (i.e. they are decrementable), then the following are all true:
  • std::addressof(--a) == std::addressof(a),
  • bool(a-- == b),
  • bool(((void)a--, a) == --b),
  • bool(++(--a) == b).
• If a and b are in the domain of both pre- and post- operator++ (i.e. they are incrementable), then bool(--(++a) == b) is true.

4) Let D denote /*iota-diff-t*/<I>. Type I models advanceable only if I satisfies advanceable and all concepts it subsumes are modeled, and given

• objects a and b of type I and
• value n of type D,

such that b is reachable from a after n applications of ++a, all following conditions are satisfied:

• (a += n) is equal to b.
• std::addressof(a += n) is equal to std::addressof(a).
• I(a + n) is equal to (a += n).
• For any two positive values x and y of type D, if I(a + D(x + y)) is well-defined, then I(a + D(x + y)) is equal to I(I(a + x) + y).
• I(a + D(0)) is equal to a.
• If I(a + D(n - 1)) is well-defined, then I(a + n) is equal to [](I c) { return ++c; }(I(a + D(n - 1))).
• (b += -n) is equal to a.
• (b -= n) is equal to a.
• std::addressof(b -= n) is equal to std::addressof(b).
• I(b - n) is equal to (b -= n).
• D(b - a) is equal to n.
• D(a - b) is equal to D(-n).
• bool(a <= b) is true.

Nested types

Type	Definition
iterator_concept	an iterator tag, see below
iterator_category (only present if W models incrementable and /*iota-diff-t*/<W> is an integral type)	std::input_iterator_tag
value_type	W
difference_type	/*iota-diff-t*/<W>

Determining the iterator concept

iterator_concept is defined as follows:

• If W models advanceable, iterator_concept denotes std::random_access_iterator_tag.
• Otherwise, if W models decrementable, iterator_concept denotes std::bidirectional_iterator_tag.
• Otherwise, if W models incrementable, iterator_concept denotes std::forward_iterator_tag.
• Otherwise, iterator_concept denotes std::input_iterator_tag.

Data members

Member	Definition
W value_	the current value (exposition-only member object*)

Member functions

std::ranges::iota_view::iterator::iterator

/*iterator*/() requires std::default_initializable<W> = default;	(1)	(since C++20)
constexpr explicit /*iterator*/( W value );	(2)	(since C++20)

1) Value initializes value_.

2) Initializes value_ with value.

std::ranges::iota_view::iterator::operator*

constexpr W operator*() const noexcept(std::is_nothrow_copy_constructible_v<W>);		(since C++20)

Returns value_.

Example

Run this code

#include <cassert>
#include <ranges>

int main()
{
    auto it{std::views::iota(6, 9).begin()};
    const int& r = *it; // binds with temporary
    assert(*it == 6 and r == 6);
    ++it;
    assert(*it == 7 and r == 6);
}

std::ranges::iota_view::iterator::operator++

constexpr /*iterator*/& operator++();	(1)	(since C++20)
constexpr void operator++(int);	(2)	(since C++20)
constexpr /*iterator*/ operator++(int) requires std::incrementable<W>;	(3)	(since C++20)

1) Equivalent to ++value_ ; return *this;.

2) Equivalent to ++value_ ;.

3) Equivalent to auto tmp = *this; ++value_ ; return tmp;.

Example

Run this code

#include <cassert>
#include <ranges>

int main()
{
    auto it{std::views::iota(8).begin()};
    assert(*it == 8);
    assert(*++it == 9);
    assert(*it++ == 9);
    assert(*it == 10);
}

std::ranges::iota_view::iterator::operator--

constexpr /*iterator*/& operator--() requires /*decrementable*/<W>;	(1)	(since C++20)
constexpr /*iterator*/operator--(int) requires /*decrementable*/<W>;	(2)	(since C++20)

1) Equivalent to --value_ ; return *this;.

2) Equivalent to auto tmp = *this; --value_ ; return tmp;.

Example

Run this code

#include <cassert>
#include <ranges>

int main()
{
    auto it{std::views::iota(8).begin()};
    assert(*it == 8);
    assert(*--it == 7);
    assert(*it-- == 7);
    assert(*it == 6);
}

std::ranges::iota_view::iterator::operator+=

constexpr /*iterator*/& operator+=( difference_type n ) requires /*advanceable*/<W>;		(since C++20)

Updates value_ and returns *this:

• If W is an unsigned-integer-like type:
  • If n is non-negative, performs value_ += static_cast<W>(n).
  • Otherwise, performs value_ -= static_cast<W>(-n).
• Otherwise, performs value_ += n.

Example

Run this code

#include <cassert>
#include <ranges>

int main()
{
    auto it{std::views::iota(5).begin()};
    assert(*it == 5);
    assert(*(it += 3) == 8);
}

std::ranges::iota_view::iterator::operator-=

constexpr /*iterator*/& operator-=( difference_type n ) requires /*advanceable*/<W>;		(since C++20)

Updates value_ and returns *this:

• If W is an unsigned-integer-like type:
  • If n is non-negative, performs value_ -= static_cast<W>(n).
  • Otherwise, performs value_ += static_cast<W>(-n).
• Otherwise, performs value_ -= n.

Example

Run this code

#include <cassert>
#include <ranges>

int main()
{
    auto it{std::views::iota(6).begin()};
    assert(*it == 6);
    assert(*(it -= -3) == 9);
}

std::ranges::iota_view::iterator::operator[]

constexpr W operator[]( difference_type n ) const requires /*advanceable*/<W>;		(since C++20)

Returns W(value_ + n).

Example

Run this code

#include <cassert>
#include <ranges>

int main()
{
    auto it{std::views::iota(6).begin()};
    assert(*it == 6);
    assert(*(it + 3) == 9);
}

Non-member functions

operator==, <, >, <=, >=, <=>(std::ranges::iota_view::iterator)

friend constexpr bool operator== ( const /*iterator*/& x, const /*iterator*/& y ) requires std::equality_comparable<W>;	(1)	(since C++20)
friend constexpr bool operator< ( const /*iterator*/& x, const /*iterator*/& y ) requires std::totally_ordered<W>;	(2)	(since C++20)
friend constexpr bool operator> ( const /*iterator*/& x, const /*iterator*/& y ) requires std::totally_ordered<W>;	(3)	(since C++20)
friend constexpr bool operator<= ( const /*iterator*/& x, const /*iterator*/& y ) requires std::totally_ordered<W>;	(4)	(since C++20)
friend constexpr bool operator>= ( const /*iterator*/& x, const /*iterator*/& y ) requires std::totally_ordered<W>;	(5)	(since C++20)
friend constexpr bool operator<=> ( const /*iterator*/& x, const /*iterator*/& y ) requires std::totally_ordered<W> && std::three_way_comparable<W>;	(6)	(since C++20)

1) Returns x.value_ == y.value_.

2) Returns x.value_ < y.value_.

3) Returns y < x.

4) Returns !(y < x).

5) Returns !(x < y).

6) Returns x.value_ <=> y.value_.

The != operator is synthesized from operator==.

These functions are not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when iterator is an associated class of the arguments.

operator+(std::ranges::iota_view::iterator)

friend constexpr /*iterator*/ operator+ ( /*iterator*/ i, difference_type n ) requires /*advanceable*/<W>;	(1)	(since C++20)
friend constexpr /*iterator*/ operator+ ( difference_type n, /*iterator*/ i ) requires /*advanceable*/<W>;	(2)	(since C++20)

Equivalent to i += n; return i;.

These functions are not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when iterator is an associated class of the arguments.

operator-(std::ranges::iota_view::iterator)

friend constexpr /*iterator*/ operator- ( /*iterator*/ i, difference_type n ) requires /*advanceable*/<W>;	(1)	(since C++20)
friend constexpr difference_type operator- ( const /*iterator*/& x, const /*iterator*/& y ) requires /*advanceable*/<W>;	(2)	(since C++20)

1) Equivalent to i -= n; return i;.

2) Let D be difference_type:

• If W is an integer-like type:
  • If W is signed-integer-like, returns D(D(x.value_ ) - D(y.value_ )).
  • Otherwise, returns y.value_ > x.value_ ? D(-D(y.value_ - x.value_ )) : D(x.value_ - y.value_ ).
• Otherwise, returns x.value_ - y.value_.

These functions are not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when iterator is an associated class of the arguments.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
P2259R1	C++20	member iterator_category is always defined	defined only if W satisfies incrementable
LWG 3580	C++20	bodies of operator+ and operator- rule out implicit move	made suitable for implicit move