std::ranges::crbegin

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

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Filesystem library (C++17)

Regular expressions library (C++11)

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Technical Specifications

 

Ranges library

Range access
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
Range primitives
iterator_tsentinel_t	range_size_trange_difference_t	range_value_t	range_reference_trange_rvalue_reference_t
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
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
Views
view_interface	subrange
Semiregular wrapper
Factories
empty_viewviews::empty	single_viewviews::single	iota_viewviews::iota	views::counted
Adaptors
views::all_tviews::all join_viewviews::join take_viewviews::take basic_istream_viewistream_view	ref_view                                split_viewviews::split take_while_viewviews::take_while elements_viewviews::elements	common_viewviews::common transform_viewviews::transform drop_viewviews::drop keys_viewviews::keys	reverse_viewviews::reverse filter_viewviews::filter drop_while_viewviews::drop_while values_viewviews::values

 

Defined in header <ranges>
inline namespace /*unspecified*/ {     inline constexpr /*unspecified*/ crbegin = /*unspecified*/; }		(since C++20) (customization point object)
Call signature
template< class T >     requires /* see below */ constexpr std::input_or_output_iterator auto crbegin(T&& t);

Returns an iterator to the first element of the const-qualified argument that is treated as a reversed sequence.

Let CT be

1. const std::remove_reference_t<T>& if the argument is a lvalue (i.e. T is an lvalue reference type),
2. const T otherwise,

a call to ranges::crbegin is expression-equivalent to ranges::rbegin(static_cast<CT&&>(t)).

The return type models std::input_or_output_iterator in both cases.

Expression-equivalent

Expression e is expression-equivalent to expression f, if e and f have the same effects, either are both potentially-throwing or are both not potentially-throwing (i.e. noexcept(e) == noexcept(f)), and either are both constant subexpressions or are both not constant subexpressions.

Customization point objects

The name ranges::crbegin denotes a customization point object, which is a const function object of a literal semiregular class type (denoted, for exposition purposes, as crbegin_ftor). All instances of crbegin_ftor are equal. Thus, ranges::crbegin can be copied freely and its copies can be used interchangeably.

Given a set of types Args..., if std::declval<Args>()... meet the requirements for arguments to ranges::crbegin above, crbegin_ftor will satisfy std::invocable<const crbegin_ftor&, Args...>. Otherwise, no function call operator of crbegin_ftor participates in overload resolution.

Example

Run this code

#include <iostream>
#include <vector>
#include <iterator>
 
int main() 
{
    std::vector<int> v = { 3, 1, 4 };
    auto vi = std::ranges::crbegin(v);
    std::cout << *vi << '\n'; 
 
    int a[] = { -5, 10, 15 };
    auto ai = std::ranges::crbegin(a);
    std::cout << *ai << '\n';
}

Output:

4
15

See also

ranges::rbegin (C++20)	returns a reverse iterator to a range (customization point object)
rbegincrbegin (C++14)	returns a reverse iterator to a container or array (function template)