add-to-set

(in-package "ACL2")

(defsection std/lists/add-to-set
  :parents (std/lists add-to-set)
  :short "Theorems about the built-in function @(tsee add-to-set)."
  (defthm true-listp-of-add-to-set-equal
    (equal (true-listp (add-to-set-equal a x)) (true-listp x)))
  (defthm true-listp-of-add-to-set-equal-type
    (implies (true-listp x) (true-listp (add-to-set-equal a x)))
    :rule-classes :type-prescription))