I'm not sure about ordinal fractions, but one way of representing that tree in J is:
'abcdeq';__ 0 1 1 1 0 Here, we have a pair of lists, the first is data, the second is structure. The structural values are the index of the parent node. This approach allows for relatively simple insertion. (Delete makes things more complex but you can get rid of indexes and perhaps even replace the corresponding data element with fill. This requires a later garbage collect operation.) Sometimes it might make things easier to have the root node be the parent of itself. Like any J implementation, scalar traversal will tend to be inefficient, but if you can operate on the structure as a whole you can get good performance. (This also suggests that inserts and deletes would ideally be done en-masse rather than bit by bit.) Now... whether a tree structure is worth implementing is another issue. For example, OS directory structures can serve as tree structures, and sometimes are a good choice. Then again ... trees are often used primarily to represent a flat list "efficiently" for a small-step-at-a-time algorithm, and that an approach based on flat lists might be more efficient if you can group up the inserts and deletes in a good way... Of course, often people use trees because it's fun to re-invent the wheel. But I guess what I'm saying is that trees can sometimes be a "code smell". Thanks, -- Raul On Thu, Dec 21, 2017 at 10:21 PM, David Lambert <[email protected]> wrote: > I'd use an index vector to store the ordinal fraction as I understand them. > Check my comprehension please. Do the ordinal fractions and tree agree? > > > c > / > b - d > / \ > a e > \ > q > > > 0 0 0 a > 0 1 0 b > 0 2 0 q > 0 1 1 c > 0 1 1 d > 0 1 2 e > > > Boxes take a long time in j because, among other things, each open box must > be type and shape and rank checked. > > Under ordinal fraction addressing scheme, is there a way to know that data > is stored internally as a regular array? Knowing the stride between items > is key to fast execution. > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
