nth (ANSI and GNU Common Lisp Document)

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#### 14.2.22 nth [Accessor]

`nth` n list ⇒ object

(setf (`nth` n list) new-object)

#### Arguments and Values::

n—a non-negative integer.

list—a list,

which might be a dotted list or a circular list.

object—an object.

new-object—an object.

#### Description::

nth locates the nth element of list, where the car of the list is the “zeroth” element.

Specifically,

     (nth n list) ≡ (car (nthcdr n list))

nth may be used to specify a place to setf.

Specifically,

     (setf (nth n list) new-object) ≡ (setf (car (nthcdr n list)) new-object)

#### Examples::

     (nth 0 '(foo bar baz)) ⇒  FOO
     (nth 1 '(foo bar baz)) ⇒  BAR
     (nth 3 '(foo bar baz)) ⇒  NIL
     (setq 0-to-3 (list 0 1 2 3)) ⇒  (0 1 2 3)
     (setf (nth 2 0-to-3) "two") ⇒  "two"
     0-to-3 ⇒  (0 1 "two" 3)

#### See Also::

elt , first , nthcdr