Add seq-do-indexed

* lisp/emacs-lisp/seq.el (seq-do-indexed): New function.
* test/lisp/emacs-lisp/seq-tests.el: Add a unit test for seq-do-indexed.

1 files changed, 15 insertions, 0 deletions

diff --git a/test/lisp/emacs-lisp/seq-tests.el b/test/lisp/emacs-lisp/seq-tests.el
index 50543de8ada..b227de36e97 100644
--- a/test/lisp/emacs-lisp/seq-tests.el
+++ b/test/lisp/emacs-lisp/seq-tests.el
@@ -107,6 +107,21 @@ Evaluate BODY for each created sequence.
                                   '(a b c d))
                  '((a 0) (b 1) (c 2) (d 3)))))
 
+(ert-deftest test-seq-do-indexed ()
+  (let ((result nil))
+    (seq-do-indexed (lambda (elt i)
+                      (add-to-list 'result (list elt i)))
+                    nil)
+    (should (equal result nil)))
+  (with-test-sequences (seq '(4 5 6))
+    (let ((result nil))
+      (seq-do-indexed (lambda (elt i)
+                        (add-to-list 'result (list elt i)))
+                      seq)
+      (should (equal (seq-elt result 0) '(6 2)))
+      (should (equal (seq-elt result 1) '(5 1)))
+      (should (equal (seq-elt result 2) '(4 0))))))
+
 (ert-deftest test-seq-filter ()
   (with-test-sequences (seq '(6 7 8 9 10))
     (should (equal (seq-filter #'test-sequences-evenp seq) '(6 8 10)))