ValueOrNone<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, and a public .value() 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 optional-like types such as
std::optional<T>
. Note it also matches
P0323 std::expected<T, E>
, which also has an optional-like interface. You may thus wish to preferentially match ValueOrError<T, E>
for any given T.
Namespace: BOOST_OUTCOME_V2_NAMESPACE::convert
Header: <boost/outcome/convert.hpp>



