Improve seq-group-by to return sequence elements in correct order

* lisp/emacs-lisp/seq.el (seq-group-by): Improves seq-group-by to
return sequence elements in correct order
* tests/automated/seq-tests.el: Update test for seq-group-by
* doc/lispref/sequences.texi (Sequence Functions): Update documentation
examples for seq-group-by

2 files changed, 16 insertions, 12 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index a6e5f59503e..ece253b1336 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2015-02-09  Nicolas Petton <nicolas@petton.fr>
+
+        * emacs-lisp/seq.el (seq-group-by): Improves seq-group-by to
+        return sequence elements in correct order.
+
 2015-02-11  Martin Rudalics  <rudalics@gmx.at>
 
         * frame.el (toggle-frame-maximized, toggle-frame-fullscreen):
diff --git a/lisp/emacs-lisp/seq.el b/lisp/emacs-lisp/seq.el
index 025d94e10b9..5fbec185b76 100644
--- a/lisp/emacs-lisp/seq.el
+++ b/lisp/emacs-lisp/seq.el
@@ -4,7 +4,7 @@
 
 ;; Author: Nicolas Petton <nicolas@petton.fr>
 ;; Keywords: sequences
-;; Version: 1.1
+;; Version: 1.1.1
 
 ;; Maintainer: emacs-devel@gnu.org
 
@@ -245,17 +245,16 @@ negative integer or 0, nil is returned."
   "Apply FUNCTION to each element of SEQ.
 Separate the elements of SEQ into an alist using the results as
 keys.  Keys are compared using `equal'."
-  (nreverse
-   (seq-reduce
-    (lambda (acc elt)
-      (let* ((key (funcall function elt))
-             (cell (assoc key acc)))
-        (if cell
-            (setcdr cell (push elt (cdr cell)))
-          (push (list key elt) acc))
-        acc))
-    seq
-    nil)))
+  (seq-reduce
+   (lambda (acc elt)
+     (let* ((key (funcall function elt))
+            (cell (assoc key acc)))
+       (if cell
+           (setcdr cell (push elt (cdr cell)))
+         (push (list key elt) acc))
+       acc))
+   (seq-reverse seq)
+   nil))
 
 (defun seq--drop-list (list n)
   "Return a list from LIST without its first N elements.