Hi, I am facing compilation error in the following code. I do understand why the error is, but I could not find a good solution. Here is my code and question explained in detail *What I want to do:* I want to store a key- value pair where both key and its respective values is unique. But After I create a map, I want to use the VALUE and get the corresponding key. Essentially the best way is a bimap. So I do the following using associative property maps. *What I did:* 1. define a bimap (my_bimap ) 2. define associative property map for left view of bimap ( right_asso_bimap ) 3. define associative property map for right view of bimap ( left_asso_bimap ) 4. fill the bimap using *left* view associative property map. i.e. *use boost::put( left_asso_bimap, key, value )* 5. Now using *right* view associative property map, retrieve key for given value i.e. use *boost::get( right_asso_bimap, value )* My main motive is to use GET and PUT helper functions for insertion and retrieval from a bimap. Use PUT to insert in LEFT BIMAP. and Use GET to retrieve from RIGHT BIMAP. I know the error is because of non-const-ness of the iterators because of which I cannot de-reference using iterators. But what would be the alternative to this ? This link here explains how to define parameters for bimap in order for iterators to be mutable. http://www.boost.org/doc/libs/1_55_0/libs/bimap/doc/html/boost_bimap/the_tut... *But I get the error below: * In file included from main.cpp:2:0: /usr/local/include/boost/property_map/property_map.hpp: In instantiation of 'boost::associative_property_map<UniquePairAssociativeContainer>::value_type& boost::associative_property_map<UniquePairAssociativeContainer>::operator[](const key_type&) const [with UniquePairAssociativeContainer = boost::bimaps::views::list_map_view<boost::bimaps::relation::member_at::right, boost::bimaps::detail::bimap_core<int, boost::bimaps::list_of<long unsigned int>, mpl_::na, mpl_::na, mpl_::na> > boost::associative_property_map<UniquePairAssociativeContainer>::reference = const int&; boost::associative_property_map<UniquePairAssociativeContainer>::value_type = const int; boost::associative_property_map<UniquePairAssociativeContainer>::key_type = long unsigned int]': /usr/local/include/boost/property_map/property_map.hpp:357:54: required from 'Reference boost::get(const boost::put_get_helper<Reference, PropertyMap>&, const K&) [with PropertyMap = boost::associative_property_map<boost::bimaps::views::list_map_view<boost::bimaps::relation::member_at::right, boost::bimaps::detail::bimap_core<int, boost::bimaps::list_of<long unsigned int>, mpl_::na, mpl_::na, mpl_::na> > > Reference = const int&; K = int]' main.cpp:41:35: required from here /usr/local/include/boost/property_map/property_map.hpp:502:20: error: no match for 'operator[]' (operand types are 'boost::associative_property_map<boost::bimaps::views::list_map_view<boost::bimaps::relation::member_at::right, boost::bimaps::detail::bimap_core<int, boost::bimaps::list_of<long unsigned int>, mpl_::na, mpl_::na, mpl_::na> > >::C {aka boost::bimaps::views::list_map_view<boost::bimaps::relation::member_at::right, boost::bimaps::detail::bimap_core<int, boost::bimaps::list_of<long unsigned int>, *mpl_::na, mpl_::na, mpl_::na> >}' and 'const key_type {aka const long unsigned int}')* *return (*m_c)[k];* ^ Here my code. You can also see the code here on this website link:* http://coliru.stacked-crooked.com/a/59cbf2c564bf22b2 <http://coliru.stacked-crooked.com/a/59cbf2c564bf22b2>* #include <boost/bimap.hpp> #include <boost/property_map/property_map.hpp> #include <boost/bimap/property_map/set_support.hpp>#include <boost/bimap/list_of.hpp>#include <iostream> using namespace boost; int main() {typedef int vertex_descriptor_t;namespace bm = boost::bimaps;typedef bm::bimap< vertex_descriptor_t, bm::list_of<size_t> > vd_idx_bimap_t;typedef boost::associative_property_map<vd_idx_bimap_t::left_map> Lasso_vd_idx_bimap_t;typedef boost::associative_property_map<vd_idx_bimap_t::right_map> Rasso_vd_idx_bimap_t; // define bimap and assoc prop map for itvd_idx_bimap_t my_bimap;Lasso_vd_idx_bimap_t Lmy_asso_bimap(my_bimap.left );Rasso_vd_idx_bimap_t Rmy_asso_bimap(my_bimap.right); typedef typename vd_idx_bimap_t::value_type value_type; my_bimap.insert( value_type( 1, 100 ) ); my_bimap.insert( value_type( 2, 200 ) ); int z = 1; std::cout << "value = " << get ( my_bimap.left, z ) << std::endl; // prints correctly value = 100 // use left asso bimap for inserting to bimap boost::put( Lmy_asso_bimap, 3, 300 ); // correct // print bimap using *left view*for(auto t = my_bimap.left.begin(); t != my_bimap.left.end(); ++t) std::cout << t->first << " " << t->second << "\n"; int y = 2;*z **= boost::get( Lmy_asso_bimap, y ); // CORRECT OUTPUT for left view * std::cout << "value = " << z << std::endl; // Use right asso bimap to get key based on supplied value y = 100;*z = boost::get( Rmy_asso_bimap, y );* *// -->> ERROR HERE for right view* std::cout << "value = " << z << std::endl; // print map again. (*right view*)for(auto t = my_bimap.right.begin(); t != my_bimap.right.end(); ++t) std::cout << t->first << " " << t->second << "\n"; } Please let me know whether this is a potential bug, or the code semantics is incorrect. Or the current library cannot support this. ? Regards, Aniket Pugaonkar -- Thanks and regards, Aniket Pugaonkar