namespace boost {
namespace bimaps {


template< class KeyType >
struct unconstrained_set_of;

struct unconstrained_set_of_relation;


} // namespace bimap
} // namespace boost

An unconstrained_set_of set view is a view with no constraints. The use of these kind of view boost the bimap performance but the view can not be accessed. An unconstrained view is an empty class.

namespace boost {
namespace bimaps {
namespace views {

template< -implementation defined parameter list- >
class -implementation defined view name-
{
    // Empty view
};

} // namespace views
} // namespace bimap
} // namespace boost

In the case of a bimap< unconstrained_set_of<Left>, ... >

In the set view:

typedef signature-compatible with relation< Left, ... > key_type;
typedef signature-compatible with relation< Left, ... > value_type;

In the left map view:

typedef  Left  key_type;
typedef  ...   mapped_type;

typedef signature-compatible with std::pair< Left, ... > value_type;

In the right map view:

typedef  ...  key_type;
typedef  Left mapped_type;

typedef signature-compatible with std::pair< ... , Left > value_type;