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std::ranges...erface::back(3) C++ Standard Libarystd::ranges...erface::back(3) NAME std::ranges::view_interface::back - std::ranges::view_interface::back Synopsis constexpr decltype(auto) back() requires ranges::bidirectional_range<D> && (1) (since C++20) ranges::common_range<D>; constexpr decltype(auto) back() const requires ranges::bidirectional_range<const D> && (2) (since C++20) ranges::common_range<const D>; The default implementation of back() member function returns the last element in the view of the derived type. Whether the element is returned by value or by reference depends on the operator* of the iterator type. 1) Let derived be static_cast<D&>(*this). Equivalent to return *ranges::prev(ranges::end(derived));. The behavior is undefined if empty() is true (i.e. the beginning iterator compares equal to the sentinel), even if the iterator obtained in the same way is dereferenceable. 2) Same as (1), except that derived is static_cast<const D&>(*this). Parameters (none) Return value The last element in the view. Notes In C++20, no type derived from std::ranges::view_interface in the standard library provides their own back() member function. However, following derived types cannot use the default implementa- tions, as they never satisfy neither bidirectional_range nor common_range: * std::ranges::basic_istream_view * std::ranges::lazy_split_view * std::ranges::split_view * std::ranges::take_while_view The inherited back() member function is available for std::ranges::empty_view, but a call to it always results in undefined behavior. Example This section is incomplete Reason: no example See also rbegin returns a reverse iterator to the beginning of a container or array crbegin (function template) (C++14) ranges::rbegin returns a reverse iterator to a range (C++20) (customization point object) ranges::crbegin returns a reverse iterator to a read-only range (C++20) (customization point object) Category: * Todo no example http://cppreference.com 2024.06.10 std::ranges...erface::back(3)
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