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22.2.4 List Selection
These procedures are used to get some information about a list, or to
retrieve one or more elements of a list.
| length lst
|
Scheme Procedure |
| scm_length (lst)
|
C Function |
|
Return the number of elements in list lst.
|
| last-pair lst
|
Scheme Procedure |
| scm_last_pair (lst)
|
C Function |
|
Return a pointer to the last pair in lst, signalling an error if
lst is circular.
|
| list-ref list k
|
Scheme Procedure |
| scm_list_ref (list, k)
|
C Function |
|
Return the kth element from list.
|
| list-tail lst k
|
Scheme Procedure |
| list-cdr-ref lst k
|
Scheme Procedure |
| scm_list_tail (lst, k)
|
C Function |
|
Return the "tail" of lst beginning with its kth element.
The first element of the list is considered to be element 0.
list-tail and list-cdr-ref are identical. It may help to
think of list-cdr-ref as accessing the kth cdr of the list,
or returning the results of cdring k times down lst.
|
| list-head lst k
|
Scheme Procedure |
| scm_list_head (lst, k)
|
C Function |
|
Copy the first k elements from lst into a new list, and
return it.
|