On 4/13/07, Neal Becker <ndbecker2@gmail.com> wrote:
I just posted something on ublas, but I think it may be of more general interest.
I have been using boost::range heavily, and find it useful for generic interfaces. I think it is also useful to have a multi-dimensional extension to range. In particular, a 2-d extension would help in creating algorithms that can accept a variety of 2-d structures.
For example, range has size, begin, end.
range2d would have size1, size2, begin1, begin2.
I think this is an interesting idea, and I've been looking into a little while. You could make this multi-dimensional not just 2d. How about something like .. // get the number of lines in the plane at index 0 of a 3d space plane_type& space_2d = span(space_3d, 0); range_size< plane_type >::type n_2d = size(space_2d); I'm not sure if span is the right name for it, and this has got to be encroaching on UBLAS' domain. But it's doable for ranges. I just tried the following, which I believe will work for arbitrary dimensions. #include <boost/preprocessor.hpp> #include <boost/range.hpp> #include <boost/utility.hpp> using namespace boost; #define RANGE_SPAN_RETURN_TYPE_OPEN(z, n, _) \ typename range_value< \ /**/ #define RANGE_SPAN_RETURN_TYPE_CLOSE(z, n, _) \
::type \ /**/
#define RANGE_SPAN_GET_OPEN(z, n, _) \ *next(begin( \ /**/ #define RANGE_SPAN_GET_CLOSE(z, n, _) \ ), BOOST_PP_CAT(i, n)) \ /**/ // RANGE_SPAN expands to something like ... // template<typename Range> // typename range_value< // typename range_value< Range >::type // >::type & // span(Range& range , const int i0 , const int i1) // { // return *next(begin( *next(begin( range ), i0) ), i1) ; // } #define RANGE_SPAN(z, n, _) \ template<typename Range> \ BOOST_PP_REPEAT(n, RANGE_SPAN_RETURN_TYPE_OPEN, _) \ Range \ BOOST_PP_REPEAT(n, RANGE_SPAN_RETURN_TYPE_CLOSE, _) \ & \ span(Range& range BOOST_PP_ENUM_TRAILING_PARAMS(n, const int i)) \ { \ return \ BOOST_PP_REPEAT(n, RANGE_SPAN_GET_OPEN, _) \ range \ BOOST_PP_REPEAT(n, RANGE_SPAN_GET_CLOSE, _) \ ; \ } \ /**/ // Overloads could be generated for larger dimensions than 3. BOOST_PP_REPEAT(3, RANGE_SPAN, _) int main() { typedef int volume_type[1][1][1]; typedef int plane_type[1][1]; typedef int line_type[1]; volume_type space_3d; plane_type& space_2d = span(space_3d, 0); range_size< plane_type >::type n_2d = size(space_2d); line_type& space_1d = span(space_3d, 0, 0); range_size< line_type >::type n_1d = size(space_1d); } Daniel