value_or_error<T>
If on C++ 20 or the Concepts TS is enabled, a boolean concept matching types with a public .has_value()
observer which returns bool
, a public .value()
observer function, and a public .error()
observer function.
If without Concepts, a static constexpr bool which is true for types matching the same requirements, using a SFINAE based emulation.
This concept matches expected-like types such as
P0323 std::expected<T, E>
, one of which is basic_result<T, E, NoValuePolicy>
. Be aware it does not differentiate between value-or-error types and value-and-error types if they present the interface matched above.
If you want a concept matching specifically basic_result<T, E, NoValuePolicy>
, see basic_result<T>
.
Namespace: BOOST_OUTCOME_V2_NAMESPACE::concepts
Header: <boost/outcome/convert.hpp>
Legacy: This was named convert::ValueOrError<T>
in Outcome v2.1 and earlier. Define BOOST_OUTCOME_ENABLE_LEGACY_SUPPORT_FOR
to 210
or lower to enable.