#### 14.2.8 rplaca, rplacd [Function]

`rplaca` cons object ⇒ cons

`rplacd` cons object ⇒ cons

#### Pronunciation::

rplaca: pronounced ,r\=e ’plak e or pronounced ,re ’plak e

rplacd: pronounced ,r\=e ’plak de or pronounced ,re ’plak de or pronounced ,r\=e ’plak d\=e or pronounced ,re ’plak d\=e

#### Arguments and Values::

cons—a cons.

object—an object.

#### Description::

rplaca replaces the car of the cons with object.

rplacd replaces the cdr of the cons with object.

#### Examples::

     (defparameter *some-list* (list* 'one 'two 'three 'four)) ⇒  *some-list*
     *some-list* ⇒  (ONE TWO THREE . FOUR)
     (rplaca *some-list* 'uno) ⇒  (UNO TWO THREE . FOUR)
     *some-list* ⇒  (UNO TWO THREE . FOUR)
     (rplacd (last *some-list*) (list 'IV)) ⇒  (THREE IV)
     *some-list* ⇒  (UNO TWO THREE IV)

#### Side Effects::

The cons is modified.

Should signal an error of type type-error if cons is not a cons.