[elpa] externals/queue 1c230d7 13/14: Implement iterator generators on collection data structures.

[Stefan Monnier]

branch: externals/queue
commit 1c230d7a92d8972957fe73e77c9b05beaae113cf
Author: Toby S. Cubitt <toby-predictive@dr-qubit.org>
Commit: Toby S. Cubitt <toby-predictive@dr-qubit.org>

    Implement iterator generators on collection data structures.
---
 queue.el | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/queue.el b/queue.el
index 4c9c954..ca9f5ab 100644
--- a/queue.el
+++ b/queue.el
@@ -1,6 +1,6 @@
 ;;; queue.el --- Queue data structure  -*- lexical-binding: t; -*-
 
-;; Copyright (C) 1991-1995, 2008-2009, 2012  Free Software Foundation, Inc
+;; Copyright (C) 1991-1995, 2008-2009, 2012, 2017  Free Software Foundation, 
Inc
 
 ;; Author: Inge Wallin <inge@lysator.liu.se>
 ;;         Toby Cubitt <toby-predictive@dr-qubit.org>
@@ -46,6 +46,11 @@
 
 (eval-when-compile (require 'cl))
 
+(defmacro queue--when-generators (then)
+  "Evaluate THEN if `generator' library is available."
+  (declare (debug t))
+  (if (require 'generator nil 'noerror) then))
+
 
 (defstruct (queue
             ;; A tagged list is the pre-defstruct representation.
@@ -144,6 +149,16 @@ order. The elements themselves are *not* copied."
        (queue-tail queue) nil))
 
 
+(queue--when-generators
+ (iter-defun queue-iter (queue)
+   "Return a queue iterator object.
+
+Calling `iter-next' on this object will retrieve the next element
+from the queue. The queue itself is not modified."
+   (let ((list (queue-head queue)))
+     (while list (iter-yield (pop list))))))
+
+
 (provide 'queue)