[ublas] functional.hpp signed unsigned div bug?

Subject: [ublas] functional.hpp signed unsigned div bug?
From: Robin Palotai (palotai.robin_at_[hidden])
Date: 2010-11-15 07:15:42

Hello,

In functional.hpp at a couple of places, for example:

        static
         BOOST_UBLAS_INLINE
         difference_type distance_i (difference_type k, size_type /* size_i */, size_type size_j) {
             return size_j != 0 ? k / size_j : 0;
         }

k [/|%] size_[i|j] is used, where k is difference_type (signed), size_x 
is size_type (unsigned). This results in promoting k to unsigned, and 
can yield very strange results when k is negative. For example, m being 
a size 2x2 ublas::matrix, m.begin1() - m.end1() yields 2147483646 instad 
of -2. Putting a static_cast<difference_type>(size_x) in functional.hpp 
seems to solve the problem.

Is this known / intended? If so, what is the rationale? If it is a bug, 
is this a valid workaround?

BR,
Robin