std::ranges::cend(3)

NAME
std::ranges::cend - std::ranges::cend

Synopsis
   Defined in header <ranges>
   Defined in header <iterator>
   inline namespace /* unspecified */ {
       inline constexpr /* unspecified */ cend = /* (since C++20)
   unspecified */; (customization point object)
   }
   Call signature
   template< class T >
       requires /* see below */ (since C++20)
   constexpr /* see below */ auto cend( T&& t );
   Returns a sentinel
   for the constant iterator
   (since C++23) indicating the end of a
   const-qualified
   (until C++23) range.
   range-begin-end.svg
   Let CT be
     * const std::remove_reference_t<T>& if the argument is an lvalue (i.e. T is
       an lvalue reference type), (until
     * const T otherwise. C++23)
   A call to ranges::cend is expression-equivalent to
   ranges::end(static_cast<CT&&>(t)).
   If the argument is an lvalue or
   ranges::enable_borrowed_range<std::remove_cv_t<T>> is true, then a call to
   ranges::cend is expression-equivalent to:
     * std::const_sentinel<decltype(U)>(U) for some expression U equivalent to (since
       ranges::end(/*possibly-const-range*/(t)). C++23)
   In all other cases, a call to ranges::cend is ill-formed, which can result in
   substitution failure when the call appears in the immediate context of a
   template instantiation.
   If ranges::cend(e) is valid for an expression e, where decltype((e)) is T, then
   CT models std::ranges::range, and
   (until C++23) std::sentinel_for<S, I> is true in all cases, where S is
   decltype(ranges::cend(e)), and I is decltype(ranges::cbegin(e)).
   Additionally, S models constant-iterator if it models input_iterator.
   (since C++23)
  Customization point objects
   The name ranges::cend denotes a customization point object, which is a const
   function object of a literal semiregular class type. For exposition purposes, the
   cv-unqualified version of its type is denoted as __cend_fn.
   All instances of __cend_fn are equal. The effects of invoking different instances of
   type __cend_fn on the same arguments are equivalent, regardless of whether the
   expression denoting the instance is an lvalue or rvalue, and is const-qualified or
   not (however, a volatile-qualified instance is not required to be invocable). Thus,
   ranges::cend 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::cend above, __cend_fn models
     * std::invocable<__cend_fn, Args...>,
     * std::invocable<const __cend_fn, Args...>,
     * std::invocable<__cend_fn&, Args...>, and
     * std::invocable<const __cend_fn&, Args...>.
   Otherwise, no function call operator of __cend_fn participates in overload
   resolution.

Example
// Run this code
 #include <algorithm>
 #include <cassert>
 #include <ranges>
 #include <vector>
 int main()
 {
     std::vector vec{3, 1, 4};
     int arr[]{5, 10, 15};
     assert(std::ranges::find(vec, 5) == std::ranges::cend(vec));
     assert(std::ranges::find(arr, 5) != std::ranges::cend(arr));
 }

See also
   ranges::end returns a sentinel indicating the end of a range
   (C++20) (customization point object)
   end
   cend returns an iterator to the end of a container or array
   (C++11) (function template)
   (C++14)