Hi, First of all thanks very much for the ICL! I'm using a boost::icl::interval_map with my own value type (struct V) and I have a custom value combining logic by passing boost::icl::inplace_et to the map and defining my own "operator&=" that provides the logic implementation. Now what happens is that my map ignores "m += make_pair(..., V())" because the default-constructed value is considered neutral due to: boost/icl/interval_base_map.hpp: ... interval_base_map<...>::_add(const segment_type& addend) { typedef typename on_absorbtion::type on_absorbtion_; ... const codomain_type& co_val = addend.second; if(on_absorbtion_::is_absorbable(co_val)) return this->_map.end(); This 'if' returns without actually modifying the map. Is there some public API that I can use to tell my map that it should not consider any value 'absorbable'? And is it a good idea to change this? Thank you, Filip