anchor.diff:          (dolist (el arr)
             (setf (aref result idx) (fn el))
             (setf idx (1+ idx)))
  -        (return result)))
  +        result))
   
       (defun member (item arr)
         "Check if ITEM is a member of ARR."
         (dolist (el arr)
           (if (= el item)
  -            (return true)))
  -      (return false))
  +            (return-from member true)))
  +      false)
   
       (defun set-difference (arr arr-to-sub)
         "Return a new array with only those elements in ARR that are not in ARR-TO-SUB."
  
positive.code:           (unless (member el arr-to-sub)
              (setf (aref result idx) el)
              (setf idx (1+ idx))))
          (return result)))
  
      (defun reduce (func list &optional init) ;; the use of init here is actually a bit broken wrt null
        (let* ((acc))
          (do* ((i (if init -1 0) (1+ i))
                (acc (if init init (elt list 0)) (func acc (elt list i))))
               ((>= i (1- (length list)))))
          (return acc)))
  
      (defun nconc (arr &rest arrs)
      (when (and arr (> (length arr) 0))
  
negative.code:         (dolist (el arr)
            (setf (aref arr idx) (fn el))
            (setf idx (1+ idx))))
        arr)
  
      (defun map (fn arr)
        "Call FN on each element in ARR and return the returned values in a new array."
  