Add seq-intersection and seq-difference to the seq library

* lisp/emacs-lisp/seq.el (seq-intersection, seq-difference): New
functions.

* test/automated/seq-tests.el: Add tests for seq-intersection and
seq-difference.

* doc/lispref/sequences.texi: Add documentation for seq-intersection
and seq-difference.

1 files changed, 26 insertions, 0 deletions

diff --git a/test/automated/seq-tests.el b/test/automated/seq-tests.el
index d3536b6f9a6..7f6e06cc4b6 100644
--- a/test/automated/seq-tests.el
+++ b/test/automated/seq-tests.el
@@ -250,5 +250,31 @@ Evaluate BODY for each created sequence.
     (should (same-contents-p list vector))
     (should (vectorp vector))))
 
+(ert-deftest test-seq-intersection ()
+  (let ((v1 [2 3 4 5])
+        (v2 [1 3 5 6 7]))
+    (should (same-contents-p (seq-intersection v1 v2)
+                             '(3 5))))
+  (let ((l1 '(2 3 4 5))
+        (l2 '(1 3 5 6 7)))
+    (should (same-contents-p (seq-intersection l1 l2)
+                             '(3 5))))
+  (let ((v1 [2 4 6])
+        (v2 [1 3 5]))
+    (should (seq-empty-p (seq-intersection v1 v2)))))
+
+(ert-deftest test-seq-difference ()
+  (let ((v1 [2 3 4 5])
+        (v2 [1 3 5 6 7]))
+    (should (same-contents-p (seq-difference v1 v2)
+                             '(2 4))))
+  (let ((l1 '(2 3 4 5))
+        (l2 '(1 3 5 6 7)))
+    (should (same-contents-p (seq-difference l1 l2)
+                             '(2 4))))
+  (let ((v1 [2 4 6])
+        (v2 [2 4 6]))
+    (should (seq-empty-p (seq-difference v1 v2)))))
+
 (provide 'seq-tests)
 ;;; seq-tests.el ends here