|  | 
boost::log::optional_manip
// In header: <boost/log/utility/manipulators/optional.hpp> template<typename OptionalT> boost::enable_if_c< !is_scalar< OptionalT >::value &&!is_array< OptionalT >::value, optional_manipulator< OptionalT, void >>::type optional_manip(OptionalT const & opt);
Optional manipulator generator function.
| ![[Note]](../../../../../../doc/src/images/note.png) | Note | 
|---|---|
| opt object must outlive the created manipulator object. | 
| Parameters: | 
 | ||
| Returns: | Manipulator to be inserted into the stream. |