std::ranges::views::iota, std::ranges::iota_view

 

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Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata 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

Range primitives
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)

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

Views
view_interface	subrange

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

Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while concat_viewviews::concat (C++26)(C++26)	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	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)

 

Defined in header <ranges>
template<std::weakly_incrementable W,          std::semiregular Bound = std::unreachable_sentinel_t>     requires __WeaklyEqualityComparableWith<W, Bound> && std::semiregular<W> class iota_view : public ranges::view_interface<iota_view<W, Bound>>	(1)	(since C++20)
namespace views {     inline constexpr /*unspecified*/ iota = /*unspecified*/; }	(2)	(since C++20)

1) A range factory that generates a sequence of elements by repeatedly incrementing an initial value. Can be either bounded or unbounded (infinite)

2) views::iota(E) and views::iota(E, F) are expression-equivalent to (has the same effect as) iota_view{E} and iota_view{E, F} respectively for any suitable subexpressions E and F

Expression-equivalent

Expression e is expression-equivalent to expression f, if

• e and f have the same effects, and
• either both are constant subexpressions or else neither is a constant subexpression, and
• either both are potentially-throwing or else neither is potentially-throwing (i.e. noexcept(e) == noexcept(f)).

Helper templates

template<std::weakly_incrementable W, std::semiregular Bound> inline constexpr bool enable_borrowed_range<ranges::iota_view<W, Bound>> = true;

This specialization of std::ranges::enable_borrowed_range makes iota_view satisfy borrowed_range.

Data members

std::ranges::iota_view::base_

W value_ = W(); /* exposition-only */

the current value

std::ranges::iota_view::bound_

Bound bound_ = Bound(); /* exposition-only */

the bound (defaults to std::unreachable_sentinel_t)

Member functions

std::ranges::iota_view::iota_view

iota_view() = default;	(1)
constexpr explicit iota_view(W value);	(2)
constexpr iota_view(std::type_identity_t<W> value,                     std::type_identity_t<Bound> bound);	(3)

1) Value-initializes value_ and bound_.

2) Initializes value_ with value and value-initializes bound_. This constructor is used to create unbounded iota_views, e.g. iota(0) yields numbers 0,1,2..., infinitely.

3) Initializes value_ with value and bound_ with bound. The behavior is undefined if std::totally_ordered_with<W, Bound> is modeled and bool(value <= bound) is false. This constructor is used to create bounded iota views, e.g. iota(10, 20) yields numbers from 10 to 19.

For (2) and (3), the behavior is undefined if the iota_view is bounded (i.e. Bound is not std::unreachable_sentinel_t) and bound_ is initialized to a value unreachable from value.

Parameters

value	-	the starting value
bound	-	the bound

std::ranges::iota_view::begin

constexpr /*iterator*/ begin() const;

Returns an iterator initialized with value_.

std::ranges::iota_view::end

constexpr auto end() const;	(1)
constexpr /*iterator*/ end() const requires std::same_as<W, Bound>;	(2)

1) Returns a sentinel of a specific type initialized with bound_ if this view is bounded, or std::unreachable_sentinel if this view is unbounded.

2) Returns an iterator initialized with bound_.

std::ranges::iota_view::size

constexpr auto size() const   requires (std::same_as<W, Bound> && __Advanceable<W>) ||            (std::integral<W> && std::integral<Bound>) ||              std::sized_sentinel_for<Bound, W> {   if constexpr (__IsIntegerLike<W> && __IsIntegerLike<Bound>)     return (value_ < 0)       ? ((bound_ < 0)         ? __MakeUnsignedLike(-value_) - __MakeUnsignedLike(-bound_)         : __MakeUnsignedLike(bound_) + __MakeUnsignedLike(-value_))       : __MakeUnsignedLike(bound_) - __MakeUnsignedLike(value_);   else     return __MakeUnsignedLike(bound_ - value_); }

Returns the size of the view if the view is bounded.

Deduction guides

template<class W, class Bound>     requires (!__IsIntegerLike<W> || !__IsIntegerLike<Bound> ||               __IsSignedIntegerLike<W> == __IsSignedIntegerLike<Bound>)   iota_view(W, Bound) -> iota_view<W, Bound>;

Note that the guide protects itself against signed/unsigned mismatch bugs, like views::iota(0, v.size()), where 0 is a (signed) int and v.size() is an (unsigned) std::size_t.

Nested classes

iterator	the iterator type (public member class)
sentinel	the sentinel type used when the iota_view is bounded and Bound and W are not the same type (public member class)

Example

Run this code

#include <ranges>
#include <iostream>
 
int main()
{
    for (int i : std::ranges::iota_view{1, 10})
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (int i : std::views::iota(1, 10))
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (int i : std::views::iota(1) | std::views::take(9))
        std::cout << i << ' ';
    std::cout << '\n';
}

Output:

1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9