From cppreference.com
Defined in header
Defined in header
inlinenamespace/* unspecified */{inlineconstexpr/* unspecified */crbegin=/* unspecified */;}(since C++20)
(customization point object)Call signature
template<classT>requires/* see below */constexpr/* see below */autocrbegin(T&&t);(since C++20)Returns an iterator to the first element of the const-qualified argument that is treated as a reversed sequence.
(until C++23)Returns a constant iterator to the first element of the argument that is treated as a reversed sequence.
(since C++23)
Let CT be
conststd::remove_reference_t<T>& if the argument is an lvalue (i.e. T is an lvalue reference type),
constT otherwise.
A call to ranges::crbegin is
to ranges::rbegin(static_cast<CT&&>(t)).
(until C++23)If the argument is an lvalue or ranges::enable_borrowed_range<std::remove_cv_t<T>> is true, then a call to ranges::crbegin is
to:
std::const_iterator<decltype(U)>(U) for some expression U equivalent to ranges::rbegin(
(t)).
In all other cases, a call to ranges::crbegin is ill-formed, which can result in
when the call appears in the immediate context of a template instantiation.
(since C++23)The return type models
and
(since C++23) in all cases.
Customization point objects
The name ranges::crbegin denotes a customization point object, which is a const
of a
class type. See
for details.
Example
Run this code
#include<cassert>#include<iterator>#include<span>#include<vector>intmain(){std::vector<int>v{3,1,4};autovi=std::ranges::crbegin(v);assert(*vi==4);++vi;// OK, iterator object is mutableassert(*vi==1);// *vi = 13; // Error: underlying element is read-onlyinta[]{-5,10,15};autoai=std::ranges::crbegin(a);assert(*ai==15);// auto x_x = std::ranges::crbegin(std::vector<int>{6, 6, 6});// ill-formed: the argument is an rvalue (see Notes ↑)autosi=std::ranges::crbegin(std::span{a});// OKassert(*si==15);static_assert(std::ranges::enable_borrowed_range<std::remove_cv_t<decltype(std::span{a})>>);}See also
(C++20)
returns a reverse iterator to a range
(customization point object)
(C++14)
returns a reverse iterator to the beginning of a container or array
(function template)