std::expected<T,E>::value
From cppreference.com
Primary template |
||
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) |
void partial specialization |
||
|
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 for void
Otherwise, throws an exception of type
std::bad_expected_access
<
std::decay_t
<E>>
that contains a copy of error()
3,4) If
std::is_copy_constructible_v<E>
or
std::is_constructible_v
<E, decltype(std::
move
(error(
)
)
)
>
is false
Return value
1,2)
val
3,4)
std::move(
val)
Exceptions
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 copy/move-constructible for overloads (5,6)
|
required |
See also
| returns the expected value if present, another value otherwise (public member function) |
|
| accesses the expected value (public member function) |
|
| returns the unexpected value (public member function) |
|
|
(C++23)
|
exception indicating checked access to an expected that contains an unexpected value (class template) |