Implement iterator generator for avl-trees.

* lisp/emacs-lisp/avl-tree.el (avl-tree-iter): New iter-defun.

1 files changed, 16 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/avl-tree.el b/lisp/emacs-lisp/avl-tree.el
index 17f1ffa9f61..32f7d2c6d8d 100644
--- a/lisp/emacs-lisp/avl-tree.el
+++ b/lisp/emacs-lisp/avl-tree.el
@@ -52,7 +52,7 @@
 ;;; Code:
 
 (eval-when-compile (require 'cl-lib))
-
+(require 'generator)
 
 
 ;; ================================================================
@@ -670,6 +670,21 @@ a null element stored in the AVL tree.)"
   (null (avl-tree--stack-store avl-tree-stack)))
 
 
+(iter-defun avl-tree-iter (tree &optional reverse)
+  "Return an AVL tree iterator object.
+
+Calling `iter-next' on this object will retrieve the next element
+from TREE. If REVERSE is non-nil, elements are returned in
+reverse order.
+
+Note that any modification to TREE *immediately* invalidates all
+iterators created from TREE before the modification (in
+particular, calling `iter-next' will give unpredictable results)."
+  (let ((stack (avl-tree-stack tree reverse)))
+    (while (not (avl-tree-stack-empty-p stack))
+      (iter-yield (avl-tree-stack-pop stack)))))
+
+
 (provide 'avl-tree)
 
 ;;; avl-tree.el ends here