[Boost-users] [containers] defining the insertion point of non-unique keys

Hi @boost, I'm looking for the solution to the following problem: there is a collection of objects and I want to find a particular object by two different keys. The first key is unique, so there is no problem. The second key however is non-unique and if I search for an object using this key I want to find the element that was inserted last in that sequence. Neither boost::multindex nor boost:intrusive seems to have solutions right at hand. If using boost::multindex I could try to insert a new element in the non-unique sequence using the lower_bound iterator of that sequence as a hint. However it is not documented that in that case the element is always inserted before the hint. Same is true for boost:intrusive::multi_set/multi_map. And I'm not able to swap the position of two adjacent elements in a multi_set or multi_map, if they have equal keys. To illustrate the problem, here is some code: struct A { int a; // non-unique key void* b; // unique key // stuff }; using namespace boost::multi_index; typedef multi_index_container >, ordered_unique > > > tCollection; void foo(tCollection& collection, int key) { typedef tCollection::nth_index<0>::type tItByInt; tItByInt i = collection.get<0>().lower_bound(key); // use the current lower bound as a hint: tItByInt insertPos = collection.get<0>.insert(i, getObject(key)); // the big question: does the assertion holds? assert(collection.get<0>().lower_bound(key) == insertPos); } Best regards Olaf Krzikalla