template< class F > constexpr optional or_else( F&& f ) const&; | (1) | (since C++23) |
template< class F > constexpr optional or_else( F&& f ) &&; | (2) | (since C++23) |
Returns *this if it contains a value. Otherwise, returns the result of f.
The program is ill-formed if std::remove_cvref_t<std::invoke_result_t<F>> is not same as std::optional<T>.
return *this ? *this : std::forward<F>(f)();. This overload participates in overload resolution only if both std::copy_constructible<T> and std::invocable<F> are modeled.return *this ? std::move(*this) : std::forward<F>(f)();. This overload participates in overload resolution only if both std::move_constructible<T> and std::invocable<F> are modeled.| f | - | a function or Callable object that returns an std::optional<T> |
*this or the result of f, as described above.
| Feature-test macro | Value | Std | Comment |
|---|---|---|---|
__cpp_lib_optional | 202110L | (C++23) |
Monadic operations in std::optional |
| returns the contained value if available, another value otherwise (public member function) |
|
|
(C++23) | returns the result of the given function on the contained value if it exists, or an empty optional otherwise (public member function) |
|
(C++23) | returns an optional containing the transformed contained value if it exists, or an empty optional otherwise (public member function) |
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