lookup

radix-tree.rkt

@@ -69,16 +69,18 @@
     [(list 'no-match node partial-key visited)
      (insert-node! node partial-key)]))
 
-(define (rt-lookup node key)
+(define (rt-lookup node key failure-result)
   (define (find-first-with-data nodes)
-    (for/first ([node nodes]
-                #:when (not (eq? empty-node-data (rt-node-data node))))
-               (rt-node-data node)))
-  (match (rt-partial-iterate node key)
-         [(list 'exact node)
-          (let ([d (rt-node-data node)])
-            (if (eq? empty-node-data d) #f d))]
-         [(list sym . rst) (find-first-with-data (last rst))]))
+    (or (for/first ([node (in-list nodes)]
+                    #:when (not (eq? empty-node-data (rt-node-data node))))
+          (rt-node-data node))
+        (failure-result)))
+  (find-first-with-data
+   (match (rt-partial-iterate node key)
+     [(list 'exact node)
+      (list node)]
+     [(list _ ... visited)
+      visited])))
 
 ; (define test (make-rt))
 ; (define (test-insert! x)
@@ -103,4 +105,4 @@
   (when edge1
     (displayln (format "~a  edge1 ~a" prefix (rt-edge-label edge1)))
     (rt-dump (rt-edge-target edge1) (string-append prefix "  "))))
-(rt-dump test)
+;(rt-dump test)