XLISP cdaar ... cdddr

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# cdaar ... cdddr

Type: | - | function (subr)
Source: | - | xllist.c

## Syntax

(cdaar expr)
(cdadr expr)
(cddar expr)
(cdddr expr)
  expr - a list or list expression
  returns - the result of the last cdr function

## Description

The 'cdaar', 'cdadr', 'cddar' and 'cdddr' functions go through the list expression and perform a sequence of car or cdr operations. The sequence of operations is performed from right to left. So 'cddar' does a car on the expression, followed by a acdr, followed by another cdr. If at any point the list is NIL, then NIL is returned. If at any point a car operation is performed on an atom [as opposed to a list] an error is signalled:

    error: bad argument

## Examples

    (setq mylist '(((11A 11B) (12A 12B) (13A 13B))
                   ((21A 21B) (22A 22B) (23A 23B))
                   ((31A 31B) (32A 32B) (33A 33B))
                   ((41A 41B) (42A 42B) (43A 43B))))

    (cdaar mylist)  => (11B)
    (cdadr mylist)  => ((22A 22B) (23A 23B))
    (cddar mylist)  => ((13A 13B))
    (cdddr mylist)  => (((41A 41B) (42A 42B) (43A 43B)))

Note: The 'c...r' functions are part of the historical Lisp functions. You may find it easier to work with the modern lisp functions like nth and nthcdr.

See also:

- Contents → List Functions
- Tutorials → Lisp Hints → List Accessors

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Nyquist / XLISP 2.0 - Contents | Tutorials | Examples | Reference