Hi John, lists, I am replying to your ticket #5207 on the lists because I am afraid that you walked into a trap that others can fall into as well. In the ITL, the precursor of Boost.ICL there was a single polymorphic interval class template: itl::interval. Due to input from the list during the review I split up this "one size fit's all" template in smaller classes according to static and dynamic interval concepts. In order to help ITL users to have a simple transition from ITL to ICL I wrote a template icl::interval. icl::interval is a meta function that yields the right interval type dependent on the instance type e.g. : BOOST_STATIC_ASSERT(( boost::is_same< interval<int>::type , discrete_interval<int> >::value )); So ITL users could move from ITL to ICL just by appending a '::type' to all occurrences of 'interval<T>' So please note that interval<myType> myInterval; can not be used as an interval type in ICL functions. Please use interval<myType>::type myInterval; or one of the specific interval types discrete_interval, continuous_interval, (dynamic borders) closed_interval, right_open_interval, left_open_interval, open_interval (static borders) e.g. discrete_interval<int> myInterval; See examples http://www.joachim-faulhaber.de/boost_icl/doc/libs/icl/doc/html/boost_icl/ex... http://www.joachim-faulhaber.de/boost_icl/doc/libs/icl/doc/html/boost_icl/ex... http://www.joachim-faulhaber.de/boost_icl/doc/libs/icl/doc/html/boost_icl/ex... and docs http://www.joachim-faulhaber.de/boost_icl/doc/libs/icl/doc/html/boost_icl/in... for more detail. This reduces John's non compilable ICL statements in the following way: BOOST_AUTO_TEST_CASE(ticket_5207) { icl::interval< int >::type int_interval; icl::interval_set< int > int_set; icl::interval_map< int, int > int_map; icl::interval_map< int, int >::element_type int_element; icl::interval_map< int, int >::segment_type int_segment; // The next 4 lines compile icl::lower( int_interval ); icl::upper( int_interval ); icl::first( int_interval ); icl::last( int_interval ); // The next 4 lines are *not* supposed to compile // according to the docs: icl::add( int_set, int_set ); icl::add( int_map, int_map ); icl::subtract( int_set, int_set ); icl::subtract( int_map, int_map ); int_set += int_interval; // compiles // Here you are right, John: // The next 4 lines should compile according // to the docs, but don't icl::disjoint( int_map, int_element ); icl::disjoint( int_map, int_segment ); icl::intersects( int_map, int_segment ); icl::intersects( int_map, int_element ); // Those four are pretty special. I doubt anyone will // use them. But I will complete the library here. } Thanks for using my library and helping to improve it. Joachim -- Interval Container Library [Boost.Icl] http://www.joachim-faulhaber.de