並行迭代

在 LOOP 中允許多個 FOR 條款。當第一個子句結束時，迴圈結束：

(loop for a in '(1 2 3 4 5)
      for b in '(a b c)
      collect (list a b))
;; Evaluates to: ((1 a) (2 b) (3 c))

確定迴圈是否應該繼續的其他子句可以組合使用：

(loop for a in '(1 2 3 4 5 6 7)
      while (< a 4)
      collect a)
;; Evaluates to: (1 2 3)

(loop for a in '(1 2 3 4 5 6 7)
      while (< a 4)
      repeat 1
      collect a)
;; Evaluates to: (1)

確定哪個列表更長，一旦知道答案就切斷迭代：

(defun longerp (list-1 list-2)
    (loop for cdr1 on list-1
          for cdr2 on list-2
          if (null cdr1) return nil
          else if (null cdr2) return t
          finally (return nil)))

編號列表的元素：

(loop for item in '(a b c d e f g)
      for x from 1
      collect (cons x item))
;; Returns ((1 . a) (2 . b) (3 . c) (4 . d) (5 . e) (6 . f) (7 . g))

確保列表中的所有數字均勻，但僅適用於前 100 個專案：

(assert
   (loop for number in list
         repeat 100
         always (evenp number)))