Add a backward-compatible version of seq-reverse

* lisp/emacs-lisp/seq.el (seq-reverse): Add a backward-compatible
version of seq-reverse that works on sequences in Emacs 24.  Bump
version to 1.2.
* test/automated/seq-tests.el (test-seq-reverse, test-seq-group-by):
Add a test for seq-reverse and update test for seq-group-by to test
vectors and strings, not only lists.

2 files changed, 32 insertions, 8 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index ece253b1336..7e45b9db64c 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,7 +1,8 @@
-2015-02-09  Nicolas Petton <nicolas@petton.fr>
+2015-02-11  Nicolas Petton <nicolas@petton.fr>
 
-        * emacs-lisp/seq.el (seq-group-by): Improves seq-group-by to
-        return sequence elements in correct order.
+        * emacs-lisp/seq.el (seq-reverse): Add a backward-compatible
+        version of seq-reverse that works on sequences in Emacs 24.
+        Bump seq.el version to 1.2.
 
 2015-02-11  Martin Rudalics  <rudalics@gmx.at>
 
@@ -74,6 +75,11 @@
         (python-shell-font-lock-turn-off): Fix typo.
         (python-util-text-properties-replace-name): Delete function.
 
+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.
+
 2015-02-09  Simen Heggestøyl  <simenheg@gmail.com>  (tiny change)
 
         * textmodes/css-mode.el (css-smie-rules): Fix paren indent (bug#19815).
diff --git a/lisp/emacs-lisp/seq.el b/lisp/emacs-lisp/seq.el
index 5fbec185b76..ad4c3536b44 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: 1.1.1
+;; Version: 1.2
 
 ;; Maintainer: emacs-devel@gnu.org
 
@@ -171,9 +171,7 @@ The result is a sequence of the same type as SEQ."
   (if (listp seq)
       (sort (seq-copy seq) pred)
     (let ((result (seq-sort pred (append seq nil))))
-      (cond ((stringp seq) (concat result))
-            ((vectorp seq) (vconcat result))
-            (t (error "Unsupported sequence: %s" seq))))))
+      (seq--into result (type-of seq)))))
 
 (defun seq-contains-p (seq elt &optional testfn)
   "Return the first element in SEQ that equals to ELT.
@@ -256,6 +254,27 @@ keys.  Keys are compared using `equal'."
    (seq-reverse seq)
    nil))
 
+(defalias 'seq-reverse
+  (if (ignore-errors (reverse [1 2]))
+      #'reverse
+    (lambda (seq)
+      "Return the reversed copy of list, vector, or string SEQ.
+See also the function `nreverse', which is used more often."
+      (let ((result '()))
+        (seq-map (lambda (elt) (push elt result))
+                 seq)
+        (if (listp seq)
+            result
+          (seq--into result (type-of seq)))))))
+
+(defun seq--into (seq type)
+  "Convert the sequence SEQ into a sequence of type TYPE."
+  (pcase type
+    (`vector (vconcat seq))
+    (`string (concat seq))
+    (`list (append seq nil))
+    (t (error "Not a sequence type name: %s" type))))
+
 (defun seq--drop-list (list n)
   "Return a list from LIST without its first N elements.
 This is an optimization for lists in `seq-drop'."
@@ -299,7 +318,6 @@ This is an optimization for lists in `seq-take-while'."
 
 (defalias 'seq-copy #'copy-sequence)
 (defalias 'seq-elt #'elt)
-(defalias 'seq-reverse #'reverse)
 (defalias 'seq-length #'length)
 (defalias 'seq-do #'mapc)
 (defalias 'seq-each #'seq-do)