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

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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

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Iterator

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decrementable

advanceable

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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)

 

iota_view() requires std::default_initializable<W> = default;	(1)	(since C++20)
constexpr explicit iota_view( W value );	(2)	(since C++20)
constexpr explicit iota_view( std::type_identity_t<W> value,                               std::type_identity_t<Bound> bound );	(3)	(since C++20)
constexpr explicit iota_view( /*iterator*/ first, /* see below */ last );	(4)	(since C++20)

Constructs an iota_view.

Overload	Data members
	value_	bound_
(1)	value-initialized	value-initialized
(2)	initialized with value
(3)		initialized with bound
(4)	initialized with first.value_	see below

2,3) If any of the following conditions is satisfied, the behavior is undefined:

• Bound() is unreachable from value, unless Bound denotes std::unreachable_sentinel_t.
• W and Bound model totally_ordered_with, and bool(value <= bound) is false.

4) If any of the following conditions is satisfied, the behavior is undefined:

• Bound() is unreachable from value, unless Bound denotes std::unreachable_sentinel_t.
• W and Bound model totally_ordered_with, and bool(first.value_ <= bound) is false.

The type of last and the method of initializing bound_ are determined by the type Bound denotes:

The type Bound denotes	The type of last	bound_
W	iterator	initialized with last.value_
std::unreachable_sentinel_t	Bound	initialized with last
any other type	sentinel	initialized with last.bound_

Parameters

value	-	the starting value
bound	-	the bound
first	-	the iterator denoting the starting value
last	-	the iterator or sentinel denoting the bound

Example

Run this code

#include <cassert>
#include <iostream>
#include <iterator>
#include <ranges>
 
int main()
{
    const auto l = {1, 2, 3, 4};
 
    auto i1 = std::ranges::iota_view<int, int>(); // overload (1)
    assert(i1.empty() and i1.size() == 0);
 
    auto i2 = std::ranges::iota_view(1); // overload (2)
    assert(not i2.empty() and i2.front() == 1);
    for (std::cout << "1) "; auto e : i2 | std::views::take(3))
        std::cout << e << ' ';
    std::cout << '\n';
 
    auto i3 = std::ranges::iota_view(std::begin(l)); // overload (2)
    assert(not i3.empty() and i3.front() == l.begin());
    for (std::cout << "2) "; auto e : i3 | std::views::take(4))
        std::cout << *e << ' ';
    std::cout << '\n';
 
    auto i4 = std::ranges::iota_view(1, 8); // overload (3)
    assert(not i4.empty() and i4.front() == 1 and i4.back() == 7);
    for (std::cout << "3) "; auto e : i4)
        std::cout << e << ' ';
    std::cout << '\n';
 
    auto i5 = std::ranges::iota_view(l.begin(), l.end()); // overload (4)
    for (std::cout << "4) "; auto e : i5)
        std::cout << *e << ' ';
    std::cout << '\n';
 
    auto i6 = std::ranges::iota_view(l.begin(), std::unreachable_sentinel); // (4)
    for (std::cout << "5) "; auto e : i6 | std::views::take(3))
        std::cout << *e << ' ';
    std::cout << '\n';
}

Output:

1) 1 2 3
2) 1 2 3 4
3) 1 2 3 4 5 6 7
4) 1 2 3 4
5) 1 2 3

Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
LWG 3523	C++20	overload (4) might use wrong sentinel type	corrected
P2711R1	C++20	overloads (3,4) were not explicit	made explicit