node->reverse-order-generator

2 files changed, 20 insertions, 7 deletions

diff --git a/mcgoron/weight-balanced-trees/internal.scm b/mcgoron/weight-balanced-trees/internal.scm
index e479649..35a25bb 100644
--- a/mcgoron/weight-balanced-trees/internal.scm
+++ b/mcgoron/weight-balanced-trees/internal.scm
@@ -436,17 +436,29 @@
           node
           (loop (insert comparator node value))))))
 
-(: node->in-order-generator (node-type -> (-> *)))
-(define (node->in-order-generator node)
+(: node->directed-generator (node-type
+                             ((struct <wb-tree>) -> node-type)
+                             ((struct <wb-tree>) -> node-type)
+                             ->
+                             (-> *)))
+(define (node->directed-generator node direction inverse-direction)
   (let ((queue (list-queue)))
-    (define (traverse-left! node)
+    (define (traverse! node)
       (when (not (null? node))
         (list-queue-add-front! queue node)
-        (traverse-left! (get-left node))))
-    (traverse-left! node)
+        (traverse! (direction node))))
+    (traverse! node)
     (lambda ()
       (if (list-queue-empty? queue)
           (eof-object)
           (let ((current (list-queue-remove-front! queue)))
-            (traverse-left! (get-right current))
+            (traverse! (inverse-direction current))
             (get-data current))))))
+
+(: node->in-order-generator (node-type -> (-> *)))
+(define (node->in-order-generator node)
+  (node->directed-generator node get-left get-right))
+
+(: node->reverse-order-generator (node-type -> (-> *)))
+(define (node->reverse-order-generator node)
+  (node->directed-generator node get-right get-left))
diff --git a/mcgoron/weight-balanced-trees/internal.sld b/mcgoron/weight-balanced-trees/internal.sld
index 930daf9..5d99d0c 100644
--- a/mcgoron/weight-balanced-trees/internal.sld
+++ b/mcgoron/weight-balanced-trees/internal.sld
@@ -37,6 +37,7 @@
           union intersection difference xor
           update insert delete
           every
-          node->generator generator->node node->in-order-generator)
+          node->generator generator->node
+          node->in-order-generator node->reverse-order-generator)
   (include "internal.scm"))