These procedures are used to get some information about a list, or to retrieve one or more elements of a list.
Return the number of elements in list lst.
Return the last pair in lst, signalling an error if lst is circular.
Return the kth element from list.
Return the "tail" of lst beginning with its kth element. The first element of the list is considered to be element 0.
list-cdr-refare identical. It may help to think of
list-cdr-refas accessing the kth cdr of the list, or returning the results of cdring k times down lst.