CLHS: Accessor NTH

#

Accessor NTH

Syntax:

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)

Side Effects: None.

Affected By: None.

Exceptional Situations: None.

See Also:

elt, first, nthcdr

Notes: None.

The following X3J13 cleanup issue, not part of the specification, applies to this section:

- DOTTED-LIST-ARGUMENTS:CLARIFY

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