foldl/foldr based enumerations

danlentz · Aug 19, 2013 · 8213f92 · 8213f92
1 parent b214e09
commit 8213f92
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diff --git a/tree-common.lisp b/tree-common.lisp
@@ -176,7 +176,16 @@
                 (kvlr (k v l r)  node
                   (fold (the-fn k v (fold base r)) l)))))     
     (fold base node)))
-
+
+(defun node/reverse-fold (fn base node)
+  (labels ((the-fn (k &optional v a)
+             (funcall (alexandria:ensure-function fn) k v a))             
+            (fold (base node)
+              (if (empty? node) base
+                (kvlr (k v l r)  node
+                  (fold (the-fn k v (fold base l)) r)))))     
+    (fold base node)))
+
 
 (defun node/iter (node fn)
   "For the side-effect, apply FN to each node of the tree rooted at NODE"

diff --git a/tree-package.lisp b/tree-package.lisp
@@ -50,6 +50,7 @@
     :node/remove-greatest
     :node/concat2
     :node/inorder-fold
+    :node/reverse-fold
     :node/iter
     :node/at-index
     :node/find