template< class F > constexpr auto transform_error( F&& f ) &; | (1) | (since C++23) |
template< class F > constexpr auto transform_error( F&& f ) const&; | (2) | (since C++23) |
template< class F > constexpr auto transform_error( F&& f ) &&; | (3) | (since C++23) |
template< class F > constexpr auto transform_error( F&& f ) const&&; | (4) | (since C++23) |
If *this contains an error value, invokes f and returns a std::expected object that contains its result; otherwise, returns a std::expected object that contains a copy of **this. The contained value (error()) is passed as an argument to f.
Let G be:
std::remove_cv_t<std::invoke_result_t<F, decltype(error())>>; std::remove_cv_t<std::invoke_result_t<F, decltype(std::move(error()))>>. G must be a valid template argument for std::unexpected. A variable of type G must be constructible from the result of invocation (but does not need to be move-constructible). The return type is std::expected<T, G>.
true
true
| f | - | a suitable function or Callable object whose call signature returns a non-reference type |
A std::expected object containing either the result of f or an expected value, as described above.
|
(C++23) | returns the expected itself if it contains an expected value; otherwise, returns the result of the given function on the unexpected value (public member function) |
|
(C++23) | returns an expected containing the transformed expected value if it exists; otherwise, returns the expected itself (public member function) |
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