Pascal J. Bourguignon wrote:

> You could slightly generalize double, and accept any atoms. This would
> allow you to simplify it.
>
> You could also use emacs and let it do the indentation for you!
>
> (defun double (object)
> (typecase object
> (cons (cons (double (car object)) (double (cdr object))))
> (number (* 2 object))
> (t object)))
>
> (mapcar (function double)
> '( () abc 123 (1 2.0 #C(3 4) a b c (5/2 6 d e f) 7 8 9) ))
> --> (NIL ABC 246 (2 4.0 #C(6 8) A B C (5 12 D E F) 14 16 18))

Why not simply

(double '(() abc 123 (1 2.0 #C(3 4) a b c (5/2 6 d e f) 7 8 9)))
===>
(NIL ABC 246 (2 4.0 #C(6 8) A B C (5 12 D E F) 14 16 18))

Scheme

(define (double obj)
(cond ((pair? obj) `(,(double (car obj)) ,@(double (cdr obj))))
((number? obj) (* 2 obj))
(#t obj)))

(double 3)
===>
6

(double '(() abc 123 (1 2.0 (3 4) a b c (5/2 6 d e f) 7 8 9)))
===>
(() abc 246 (2 4.0 (6 8) a b c (5 12 d e f) 14 16 18))