...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Unconstrained sets allow the user to disable one of the views of a bimap. Doing so makes the bimap operations execute faster and reduces memory consumption. This completes the bidirectional mapping framework by including unidirectional mappings as a particular case.
Unconstrained sets are useful for the following reasons:
typedef
.
Given this bimap instance,
typedef bimap< std::string, unconstrained_set_of<int> > bm_type; typedef bm_type::left_map map_type; bm_type bm; map_type & m = bm.left;
or this standard map one
typedef std::map< std::string, int > map_type; map_type m;
The following code snippet is valid
m["one"] = 1; assert( m.find("one") != m.end() ); for( map_type::iterator i = m.begin(), iend = m.end(); i != iend; ++i ) { ++(i->second); } m.erase("one");
But using a bimap has some benefits
typedef map_type::const_iterator const_iterator; typedef std::pair<const_iterator,const_iterator> const_range; const_range r = m.range( "one" <= _key, _key <= "two" ); for( const_iterator i = r.first; i != r.second; ++i ) { std::cout << i->first << "-->" << i->second << std::endl; } m.modify_key( m.begin(), _key = "1" );