Next: Cutting and Pasting Lists, Previous: Construction of Lists, Up: Lists [Contents][Index]
Returns #t if object is a proper list, otherwise returns
#f. By definition, all proper lists have finite length and are
terminated by the empty list. If object is a circular list,
returns #f.
Any object satisfying this predicate will also satisfy exactly one
of pair? or null?.
(list? (list 'a 'b 'c)) ⇒ #t (list? (cons* 'a 'b 'c)) error→ (list? (circular-list 'a 'b 'c)) ⇒ #f
Returns #t if object is a circular
list, otherwise returns #f.
(circular-list? (list 'a 'b 'c)) ⇒ #f (circular-list? (cons* 'a 'b 'c)) ⇒ #f (circular-list? (circular-list 'a 'b 'c)) ⇒ #t
Returns #t if object is an improper
list, otherwise returns #f.
(dotted-list? (list 'a 'b 'c)) ⇒ #f (dotted-list? (cons* 'a 'b 'c)) ⇒ #t (dotted-list? (circular-list 'a 'b 'c)) ⇒ #f
Returns the length of list. Signals an error if list isn’t a proper list.
(length (list 'a 'b 'c)) ⇒ 3 (length (cons* 'a 'b 'c)) error→ (length (circular-list 'a 'b 'c)) error→
Clist must be a proper or circular list. If clist is a
circular list, returns #f, otherwise returns the number of
pairs comprising the list (which is the same as the length for a
proper list).
(length+ (list 'a 'b 'c)) ⇒ 3 (length+ (cons* 'a 'b 'c)) error→ (length+ (circular-list 'a 'b 'c)) ⇒ #f
Counts the number of pairs in a list-like object. If
object is a proper list, returns the same value as
length. If object is a dotted list, returns the number
of pairs including the last one. If object is a circular list,
counts the number of pairs up to and including the one with the
backwards link. If object is any other object, returns 0
as apropriate for an empty dotted list.
(count-pairs (list 'a 'b 'c)) ⇒ 3 (count-pairs (cons* 'a 'b 'c)) ⇒ 2 (count-pairs (circular-list 'a 'b 'c)) ⇒ 3
Returns #t if object is the empty list; otherwise returns
#f.
(null? '()) ⇒ #t (null? (list 'a 'b 'c)) ⇒ #f (null? (cons* 'a 'b 'c)) ⇒ #f (null? (circular-list 'a 'b 'c)) ⇒ #f
List is a proper or circular list. This procedure returns
#t if the argument is the empty list (), and #f
if the argument is a pair. It is an error to pass this procedure any
other value. This procedure is recommended as the termination
condition for list-processing procedures that are not defined on
dotted lists.
Returns the kth element of list, using zero-origin indexing.
The valid indexes of a list are the exact non-negative integers
less than the length of the list. The first element of a list has index
0, the second has index 1, and so on.
(list-ref '(a b c d) 2) ⇒ c
(list-ref '(a b c d)
(exact (round 1.8)))
⇒ c
(list-ref list k) is equivalent to
(car (drop list k)).
Returns the specified element of list. It is an error if
list is not long enough to contain the specified element (for
example, if the argument to seventh is a list that contains only
six elements).
Next: Cutting and Pasting Lists, Previous: Construction of Lists, Up: Lists [Contents][Index]