2011/2/17 John Reid <j.reid@mail.cryst.bbk.ac.uk>:
cardinality( interval< float >( 1, 5 ) ) == 18446744073709551615
Can this be true?
No, the only truth is 42 ;)
Is this by design?
Yes it is. cardinality(x) gives the number of elements in a set, container or interval. In the STL the number of elements of a container is represented by the type std::size_t. For an interval representing a set we face the situation that the number of elements can be infinite if the element type is continuous. Since float represents a real number it is assumed to be continuous. So the cardinality of interval<float>::closed(1,5) is infinite. Since std::size_t has no INF value, I chose (std::numeric_limits<std::size_t>::max)() as representation for infinity. You can use icl::infinity<T>::value() to check for this representation of infinity. typedef size_type_of<interval<float>::type>::type itv_float_size_type; BOOST_CHECK( (is_same<itv_float_size_type, std::size_t>::value) ); BOOST_CHECK_EQUAL(cardinality(interval<float>::closed(5,5)), 1); BOOST_CHECK_EQUAL( cardinality(interval<float>::closed(1,5)), icl::infinity<itv_float_size_type>::value() ); I know ... this design is questionable. I could write a function template template<class IntervalT> boost is_infinite(IntervalT const&); and make the cardinality function partial instead. Are you using the cardinality function on float intervals in real use cases? Best regards, Joachim -- Interval Container Library [Boost.Icl] http://www.joachim-faulhaber.de