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std::expected::value(3) C++ Standard Libary std::expected::value(3) NAME std::expected::value - std::expected::value Synopsis T is not (possibly cv-qualified) void constexpr T& value() &; (1) (since C++23) constexpr const T& value() const&; (2) (since C++23) constexpr T&& value() &&; (3) (since C++23) constexpr const T&& value() const&&; (4) (since C++23) T is (possibly cv-qualified) void constexpr void value() const&; (5) (since C++23) constexpr void value() &&; (6) (since C++23) If *this contains an expected value, returns a reference to the con- tained value. Returns nothing if T is (possibly cv-qualified) void. Otherwise, throws an exception of type std::bad_expected_ac- cess<std::decay_t<E>> that contains a copy of error(). 1,2) If std::is_copy_constructible_v<E> is false, the program is ill-formed. 3,4) If std::is_copy_constructible_v<E> or std::is_con- structible_v<E, decltype(std::move(error()))> is false, the program is ill-formed. 5) If std::is_copy_constructible_v<E> is false, the program is ill- formed. 6) If std::is_move_constructible_v<E> is false, the program is ill- formed. Parameters (none) Return value 1-4) The expected value contained in *this. 5,6) (none) Exceptions 1,2,5) Throws std::bad_expected_access(std::as_const(error())) if *this contains an unexpected value. 3,4,6) Throws std::bad_expected_access(std::move(error())) if *this contains an unexpected value. Example This section is incomplete Reason: no example Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 3940 C++23 E was not required to be required copy/move-constructible for overloads (5,6) See also value_or returns the expected value if present, another value otherwise (public member function) operator-> accesses the expected value operator* (public member function) error returns the unexpected value (public member function) bad_expected_access exception indicating checked access to an ex- pected that contains (C++23) an unexpected value (class template) Category: * Todo no example http://cppreference.com 2024.06.10 std::expected::value(3)
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