On Fri, 13 Apr 2007 20:26:17 +0200, Daniel Walker <daniel.j.walker@gmail.com> wrote:
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.
Mathematically speaking, the term "span" is inappropriate: span is usually used in linear algebra to denote the space generated by all linear combinations of a set of vectors; so if you have two indipendent vectors belonging to the plane they generate the whole plane (they are a system of generators for the plane). On the contrary you do not want to expand space_3d. The right term, IMHO, could be "slice" because you want to slice space_3d in order to get one of its affine subspace. Marco -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/