On Sun, Oct 25, 2009 at 10:08 PM, John Harrop <[email protected]> wrote:
>
> 4 public class NodeCounter {
> 8 public static int countNodes (Object data) {
> 10 if (!(data instanceof Iterable)) return 1;
> 5 int result = 1;
> 8 for (Object e : (Iterable)data) {
> 6 result += countNodes(e);
> 0 }
> 3 return result;
> 0 }
> 0 }
> ------
> 44
>
> This is actually slightly better than the loop/recur version in Clojure,
> despite the types everywhere, probably because of the for-each loop being a
> bit more abstract than loop/recur (a while with an explicit iterator would
> perhaps be a fairer comparison; and map + reduce is clearly much more
> abstract still) and the use of recursion. It would surely blow up to 60 or
> even 70 if we added explicit stack management to traverse the tree
> non-recursively and used a while loop with an explicit iterator.
>
It's worse than I thought:
4 public class NodeCounter {
8 public static int countNodes (Object data) {
7 LinkedList stack = new LinkedList();
6 stack.add(data);
5 int result = 1;
9 while (!(stack.isEmpty())) {
3 result++;
8 Object front = stack.getFirst();
6 if (front instanceof Iterable) {
10 Iterator i = ((Iterable)front).iterator();
6 while (i.hasNext())
9 stack.addFirst(i.next());
0 }
0 }
3 return result;
0 }
0 }
----
84
This is the closest possible Java to the loop-recur implementation. It's
about 68% larger in complexity by the AST-size metric.
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