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 contained value.
Returns nothing if T is (possibly cv-qualified) void.

Otherwise, throws an exception of type std::bad_expected_access<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_constructible_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 retroactively 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 expected that contains
(C++23) an unexpected value
(class template)

Category:¶

* Todo no example