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| ANSI Common Lisp 14 Conses 14.2 Dictionary of Conses
14.2.29 last | Function
  Syntax: last list `&optional` n tail Arguments and Values: list - a list, which might be a dotted list but must not be a circular list. n - a non-negative integer. The default is `1`. tail - an object. Description: last returns the last n conses (not the last n elements) of list). If list is `()`, last returns `()`. If n is zero, the atom that terminates list is returned. If n is greater than or equal to the number of cons cells in list, the result is list. Examples:
       (last nil)   NIL
       (last '(1 2 3))  (3)
       (last '(1 2 . 3))  (2 . 3)
       (setq x (list 'a 'b 'c 'd))  (A B C D)
       (last x)  (D)
       (rplacd (last x) (list 'e 'f)) x  (A B C D E F)
       (last x)  (F)

       (last '(a b c))    (C)

       (last '(a b c) 0)  ()
       (last '(a b c) 1)  (C)
       (last '(a b c) 2)  (B C)
       (last '(a b c) 3)  (A B C)
       (last '(a b c) 4)  (A B C)

       (last '(a . b) 0)   B
       (last '(a . b) 1)  (A . B)
       (last '(a . b) 2)  (A . B)
  Exceptional Situations: The consequences are undefined if list is a circular list. Should signal an error of type type-error if n is not a non-negative integer. See Also: butlast, nth Notes: The following code could be used to define last.
       (defun last (list &optional (n 1))
         (check-type n (integer 0))
         (do ((l list (cdr l))
              (r list)
              (i 0 (+ i 1)))
             ((atom l) r)
           (if (>= i n) (pop r))))
Allegro CL Implementation Details: None.

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