for (node = rand () % 2 ? range_set_first (rs) : range_set_next (rs, NULL),
start = width = 0;
next_region (pattern, start + width, &start, &width);
for (node = rand () % 2 ? range_set_first (rs) : range_set_next (rs, NULL),
start = width = 0;
next_region (pattern, start + width, &start, &width);