;;; Procedure:
;;;   snoc
;;; Parameters:
;;;   lst, a list
;;;   val, any kind of value
;;; Purpose:
;;;   Add val to the end of lst
;;; Produces:
;;;   newlst, a list
;;; Preconditions:
;;;   [Standard]
;;; Postconditions:
;;;   (list-ref newlst pos) = (list-ref lst pos) for all positions in lst.
;;;   (list-ref newlst (length lst)) = val
(define snoc
  (lambda (lst val)
    (append lst (list val))))