(2) Generalization of "find" in the Set view and the STL/iterator view. 2011/2/23 John Reid <j.reid@mail.cryst.bbk.ac.uk>:
On 22/02/11 20:03, Joachim Faulhaber wrote:
2011/2/22 John Reid<j.reid@mail.cryst.bbk.ac.uk>
interval_map::find is a pretty late addition to ITL/ICL, because using find in the STL way makes little sense on interval containers most of the time. We can not "find" an large interval in an icl::interval_set of small intervals.
{[0,2),[5,7)}.find([0,9))
If we cannot find the large interval, isn't the end() iterator a suitable return value to suggest it was not in the set/map?
This is a question of design decisions of course. On the one hand I view intervals as Sets and also interval_set implements Set. (Capital S for concept Set). In this view, it is unusual to ask whether a set is found in a set, because one is not intended to be the element of the other. I this view (the Set view) we can achieve everything we need using predicates contains, intersects and functions add_intersection, &= and & (intersection) http://www.boost.org/doc/libs/1_46_0/libs/icl/doc/html/boost_icl/function_re... On the other hand, but with a lower priority in my design, I am supporting functions using iterators that are common to STL containers and that will be expected by users. 'find' is only defined on element_types, because only element can be "found" in sets. All functionality related to a "generalized find" in the STL/iterator related view can be provided by the member functions lower_bound, upper_bound and equal_range that are common to STL interfaces of associative containers: http://www.boost.org/doc/libs/1_46_0/libs/icl/doc/html/boost_icl/function_re... Here is some code for clarification: BOOST_AUTO_TEST_CASE(generalized_find) { typedef icl::interval_set<int>::iterator int_set_iterator; icl::interval_set<int> int_set; icl::interval<int>::type to_be_found(1,5); int_set += icl::interval<int>::type(0,2); int_set += icl::interval<int>::type(4,7); int_set += icl::interval<int>::type(8,9); int_set_iterator found; found = int_set.lower_bound(to_be_found); cout << *found << endl; // [0,2) found = int_set.upper_bound(to_be_found); cout << *found << endl; // [8,9) std::pair<int_set_iterator,int_set_iterator> exterior; exterior = int_set.equal_range(to_be_found); cout << "[" << *exterior.first << "," << *exterior.second << ")" << endl; // [[0,2),[8,9)) } It's good you brought up this question, so I could clarify the design decisions here. Thanks, Joachim -- Interval Container Library [Boost.Icl] http://www.joachim-faulhaber.de