caaar caadr cadar caddr
type: function (subr) location: built-in source file: xllist.c Common LISP compatible: yes supported on: all machines
SYNTAX
(caaar <expr> )
(caadr <expr> )
(cadar <expr> )
(caddr <expr> )
<expr> - a list or list expression
DESCRIPTION
The CAAAR, CAADR, CADAR and CADDR functions go through the list expression and perform a sequence of CAR/CDR operations. The sequence of operations is performed from right to left. So CADDR does a CDR on the expression, followed by a CDR, followed by a CAR. If at any point the list is NIL, NIL is returned. If at any point a CAR operation is performed on an atom (as opposed to a list) an error is reported - "error: BAD ARGUMENT".
EXAMPLES
(setq mylist '( ( (a b) (c d) (e f) ) ; make a 3-level list
( (g h) (i j) (k l) )
( (m n) (o p) (q r) )
( (s t) (u v) (w x) )
) )
(caaar mylist) ; returns A
(caadr mylist) ; returns (G H)
(cadar mylist) ; returns (C D)
(caddr mylist) ; returns ((M N) (O P) (Q R))
(cdaar mylist) ; returns (B)
(cdadr mylist) ; returns ((I J) (K L))
(cddar mylist) ; returns ((E F))
(cdddr mylist) ; returns (((S T) (U V) (W X)))