template< class F > constexpr auto or_else( F&& f ) &; | (1) | (since C++23) |
template< class F > constexpr auto or_else( F&& f ) const&; | (2) | (since C++23) |
template< class F > constexpr auto or_else( F&& f ) &&; | (3) | (since C++23) |
template< class F > constexpr auto or_else( F&& f ) const&&; | (4) | (since C++23) |
If *this contains an error value, invokes f and returns its result; otherwise, returns a std::expected object that contains a copy of value(). The contained value (error()) is passed as an argument to f.
Let G be:
std::remove_cvref_t<std::invoke_result_t<F, decltype(error())>>; std::remove_cvref_t<std::invoke_result_t<F, decltype(std::move(error()))>>. The return type is G, which must be a specialization of std::expected, and std::is_same_v<G::value_type, T> must be true.
true
true
| f | - | a suitable function or Callable object that returns a std::expected |
The result of f, or a std::expected object that contains a copy of the expected value, as described above.
| Feature-test macro | Value | Std | Comment |
|---|---|---|---|
__cpp_lib_expected | 202211L | (C++23) | Monadic functions for std::expected |
|
(C++23) | returns the expected itself if it contains an expected value; otherwise, returns an expected containing the transformed unexpected value (public member function) |
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