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This is example 4 in Boost.MultiIndex documentation.
This example shows how to construct a bidirectional map with multi_index_container.
By a bidirectional map we mean a container of elements of std::pair<const FromType,const ToType>
such that no two elements exists with
the same first or second value (std::map
only
guarantees uniqueness of the first member). Fast look-up is provided for
both keys. The program features a tiny Spanish-English dictionary with on-line
query of words in both languages.
#include <iostream> #include <boost/tokenizer.hpp> #include <boost/multi_index_container.hpp> #include <boost/multi_index/key_extractors.hpp> #include <boost/multi_index/ordered_index.hpp> using namespace boost; using namespace boost::multi_index; // tags for accessing both sides of a bidirectional map struct from {}; struct to {}; // The class template bidirectional_map wraps the specification // of a bidirectional map based on multi_index_container. template<typename FromType,typename ToType> struct bidirectional_map { typedef std::pair<FromType,ToType> value_type; typedef multi_index_container< value_type, indexed_by < ordered_unique < tag<from>, member<value_type,FromType,&value_type::first> >, ordered_unique < tag<to>, member<value_type,ToType,&value_type::second> > > > type; }; // A dictionary is a bidirectional map from strings to strings typedef bidirectional_map<std::string,std::string>::type dictionary; int main() { dictionary d; // Fill up our microdictionary. // first members Spanish, second members English. d.insert(dictionary::value_type("hola","hello")); d.insert(dictionary::value_type("adios","goodbye")); d.insert(dictionary::value_type("rosa","rose")); d.insert(dictionary::value_type("mesa","table")); std::cout << "enter a word" << std::endl; std::string word; std::getline(std::cin,word); // search the queried word on the from index (Spanish) dictionary::iterator it = d.get<from>().find(word); if( it != d.end() ) { // the second part of the element is the equivalent in English std::cout << word << " is said " << it->second << " in English" << std::endl; } else { // word not found in Spanish, try our luck in English dictionary::index_iterator<to>::type it2 = d.get<to>().find(word); if( it2 != d.get<to>().end() ) { std::cout << word << " is said " << it2->first << " in Spanish" << std::endl; } else { std::cout << "No such word in the dictionary" << std::endl; } } return 0; }
#include <iostream> #include <boost/tokenizer.hpp> #include <boost/bimap/bimap.hpp> using namespace boost::bimaps; // A dictionary is a bidirectional map from strings to strings typedef bimap<std::string,std::string> dictionary; typedef dictionary::value_type translation; int main() { dictionary d; // Fill up our microdictionary. // first members Spanish, second members English. d.insert( translation("hola" ,"hello" )); d.insert( translation("adios","goodbye")); d.insert( translation("rosa" ,"rose" )); d.insert( translation("mesa" ,"table" )); std::cout << "enter a word" << std::endl; std::string word; std::getline(std::cin,word); // search the queried word on the from index (Spanish) dictionary::left_const_iterator it = d.left.find(word); if( it != d.left.end() ) { // the second part of the element is the equivalent in English std::cout << word << " is said " << it->second<< " in English" << std::endl; } else { // word not found in Spanish, try our luck in English dictionary::right_const_iterator it2 = d.right.find(word); if( it2 != d.right.end() ) { std::cout << word << " is said " << it2->second
<< " in Spanish" << std::endl; } else { std::cout << "No such word in the dictionary" << std::endl; } } return 0; }
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Or better, using tags...
#include <iostream> #include <boost/bimap/bimap.hpp> using namespace boost::bimaps; // tags struct spanish {}; struct english {}; // A dictionary is a bidirectional map from strings to strings typedef bimap < tagged< std::string,spanish >, tagged< std::string,english > > dictionary; typedef dictionary::value_type translation; int main() { dictionary d; // Fill up our microdictionary. // first members Spanish, second members English. d.insert( translation("hola" ,"hello" )); d.insert( translation("adios","goodbye")); d.insert( translation("rosa" ,"rose" )); d.insert( translation("mesa" ,"table" )); std::cout << "enter a word" << std::endl; std::string word; std::getline(std::cin,word); // search the queried word on the from index (Spanish) */ dictionary::map_by<spanish>::const_iterator it = d.by<spanish>().find(word); if( it != d.by<spanish>().end() ) { std::cout << word << " is said " << it->get<english>() << " in English" << std::endl; } else { // word not found in Spanish, try our luck in English dictionary::map_by<english>::const_iterator it2 = d.by<english>().find(word); if( it2 != d.by<english>().end() ) { std::cout << word << " is said " << it2->get<spanish>() << " in Spanish" << std::endl; } else { std::cout << "No such word in the dictionary" << std::endl; } } return 0; }