It is often the case that one is dealing with key value pairs when using the STL containers. Sometimes, I have found the need to extract either the key or the value from these pairs as part of a call to a standard C++ algorithm. Unfortunatelly, unless one is using the SGI implementation of STL, function objects such as select1st and select2nd are not available. So, I started to look for a boost equivalent and finally found it in the bind library. Here are the mechanisms, with the std prefix omitted for brevity: Given: MyMap mymap; // A map of some key type to some value type MyVector myvector; // A vector of elements either of key type or value type, depending on requirements --- // Copy all keys from the map to the vector, which is assumed to containe elements of key type: // Implementation using select1st, when available (e.g. SGI STL extensions) transform(mymap.begin(),mymap.end(),back_inserter(myvector),select1st<MyMap::value_type>()); // Implementation using boost::bind transform(mymap.begin(),mymap.end(),back_inserter(myvector),boost::bind(&MyMap::value_type::first,_1)); // Copy all keys from the map to the vector, which, in this case, is assumed to containe elements of value type: // Implementation using select2nd, when available transform(mymap.begin(),mymap.end(),back_inserter(myvector),select2nd<MyMap::value_type>()); // Implementation using boost::bind transform(mymap.begin(),mymap.end(),back_inserter(myvector),boost::bind(&MyMap::value_type::second,_1)); --- I hope this helps anyone else that needs similar functionality and doesn't want to reinvent the wheel. Thanks, Michael Goldshteyn