6.4.4 List accessors and modifiers

Function: car pair

Function: cdr pair

[R5RS] Returns car and cdr of pair, respectively.

Function: set-car! pair obj

Function: set-cdr! pair obj

[R5RS] Modifies car and cdr of pair, by obj, respectively.

Note: (setter car) == set-car!, and (setter cdr) == set-cdr!.

Function: caar pair

Function: cadr pair

...

Function: cdddar pair

Function: cddddr pair

[R5RS] caar == (car (car x)), cadr == (car (cdr x)), and so on.

The corresponding setters are also defined.

(let ((x (list 1 2 3 4 5))) (set! (caddr x) -1) x) => (1 2 -1 4 5)

Function: length list

[R5RS] Returns the length of a proper list list. If list is a dotted list, an error is signalled. If list is a circular list, this function diverges.

If you want to handle circular lists as well, See length+ in 10.2.4 List miscellaneous routines.

Function: list-tail list k

[R5RS] Returns k-th cdr of list. list can be a proper, dotted or circular list.

Function: list-ref list k &optional fallback

[R5RS+] Returns k-th element of list. list can be a proper, dotted or circular list.

By default, list-ref signals an error if k is negative, or greater than or equal to the length of list. However, if an optional argument fallback is given, it is returned for such case. This is an extension of Gauche.

Function: last-pair list

[SRFI-1] Returns the last pair of list. list can be a proper or dotted list.