Add seq-set-equal-p to test for set equality

* lisp/emacs-lisp/seq.el (seq-set-equal-p): Add function to compare
  two lists as if they were sets.

* test/lisp/emacs-lisp/seq-tests.el (test-seq-set-equal-p): Add test
  for seq-set-equal-p.

1 files changed, 3 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index d79eecf7676..73c088c962e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -899,6 +899,9 @@ instead of its first.
 
 * Lisp Changes in Emacs 26.1
 
+** New function 'seq-set-equal-p' to check if SEQUENCE1 and SEQUENCE2
+contain the same elements, regardless of the order.
+
 +++
 ** Emacs now supports records for user-defined types, via the new
 functions 'make-record', 'record', and 'recordp'.  Records are now