append with first argument optional nil

[HPW]

Attempt to made a more alisp compatibel append:

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(define (append-nil alist )
(if alist
(begin
(setq _nlst alist)
(dolist (_lst (args))(setq _nlst(append _nlst _lst))))
(begin
(setq _nlst (list ))
(dolist (_lst (args))(setq _nlst(append _nlst _lst))))
))


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> (setq a '(1 2))
(1 2)
> (append-nil a '(3)'(4)'(5))
(1 2 3 4 5)
> (append-nil b '(3)'(4)'(5))
(3 4 5)
>


Any better solution?

[Lutz]

Use 'apply append' instead of 'dolist':

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(define (append-nil alist)
  (if alist (append alist (apply append (args)))
            (apply append (args))))


Lutz

[HPW]

Thanks a lot. I have still the problem, to get the brain more lispisch.

;-)

[Lutz]

we can make it even shorter:

Code Select Expand


(define (append-nil alist)
  (append (if alist alist '()) (apply append (args))))


Lutz