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From: Michael Heerdegen <michael_heerdegen@web.de>
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Subject: Re: Surprising behaviour of 'append' with strings
Date: Sun, 06 Nov 2022 21:33:38 +0100
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"R. Diez" <rdiezmail-emacs@yahoo.de> writes:

> I need a routine like this:
>
> (my-append
>   "1"
>   (list "2" "3")
>   "4"
> )
>
> The result should be:
>  ("1" "2" "3" "4")

(defun my-append (&rest args)
  (cl-mapcan (lambda (x) (if (consp x) x (list x)))
             args))

> As a bonus, 'my-append' should check that all elements are strings, or
> list of strings (no nested lists, and no other data types).

Use `cl-every' on the result of `my-append' with a `stringp' predicate.

Michael.