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, 6 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/seq.el b/lisp/emacs-lisp/seq.el
index 10de2484798..963a1ddf964 100644
--- a/lisp/emacs-lisp/seq.el
+++ b/lisp/emacs-lisp/seq.el
@@ -355,6 +355,12 @@ Equality is defined by TESTFN if non-nil or by `equal' if nil."
                 e))
             sequence))
 
+(cl-defgeneric seq-set-equal-p (sequence1 sequence2 &optional testfn)
+  "Return non-nil if SEQUENCE1 and SEQUENCE2 contain the same elements, regardless of order.
+Equality is defined by TESTFN if non-nil or by `equal' if nil."
+  (and (seq-every-p (lambda (item1) (seq-contains sequence2 item1 testfn)) sequence1)
+       (seq-every-p (lambda (item2) (seq-contains sequence1 item2 testfn)) sequence2)))
+
 (cl-defgeneric seq-position (sequence elt &optional testfn)
   "Return the index of the first element in SEQUENCE that is equal to ELT.
 Equality is defined by TESTFN if non-nil or by `equal' if nil."