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std::ranges...face::front(3) C++ Standard Libary std::ranges...face::front(3) NAME std::ranges::view_interface::front - std::ranges::view_interface::front Synopsis constexpr decltype(auto) front() (1) (since C++20) requires ranges::forward_range<D>; constexpr decltype(auto) front() const (2) (since C++20) requires ranges::forward_range<const D>; The default implementation of front() member function returns the first 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::begin(derived);. The behavior is undefined if empty() is true (i.e. the beginning iterator compares equal to the sentinel), even if the it- erator 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 first element in the view. Notes In C++20, no type derived from std::ranges::view_interface in the standard library provides their own front() member function. Almost all of these types use the default implementation. A notable exception is std::ranges::basic_istream_view. For it never satisfies forward_range, the view cannot use the inherited front(). The inherited front() 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 begin cbegin returns an iterator to the beginning of a container or array (C++11) (function template) (C++14) ranges::begin returns an iterator to the beginning of a range (C++20) (customization point object) ranges::cbegin returns an iterator to the beginning of a read-only range (C++20) (customization point object) Category: * Todo no example http://cppreference.com 2024.06.10 std::ranges...face::front(3)
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