XLISP caar, cadr

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

# caar, cadr

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

## Syntax

(caar expr)
(cadr expr)
  expr - a list expression
  returns - the result of the last car function

## Description

The 'caar' and 'cadr' 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 'cadr' does a cdr on the expression, followed by a car. 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

The 'cadr' function returns the same result as the second function.

## Examples

    (setq mylist '((1A 1B) (2A 2B) (3A 3B)))

    (caar mylist)  => 1A
    (cadr mylist)  => (2A 2B)

    (caar 'a)      => error: bad argument
    (caar nil)     => NIL

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