Function template optional

Function template optional_manip

boost::log::optional_manip

Synopsis

// In header: <boost/log/utility/manipulators/optional.hpp>


template<typename OptionalT, typename NoneElementT, std::size_t N> 
  boost::enable_if_c< !is_scalar< OptionalT >::value &&!is_array< OptionalT >::value, optional_manipulator< OptionalT, NoneElementT * >>::type 
  optional_manip(OptionalT const & opt, NoneElementT(&) none);

Description

Optional manipulator generator function.

	Note
	Both opt and none objects must outlive the created manipulator object.

Parameters:

`none`	Marker used to indicate when the value is not present. Optional. If not specified, nothing is output if the value is not present.
`opt`	Optional value to output. The optional value must support contextual conversion to `bool` and dereferencing, and its dereferencing result must support stream output.

Returns:

Manipulator to be inserted into the stream.