Re: Testing whether a list contains at least one non-nil element

[Jean Louis <bugs@gnu.support>]

* Emanuel Berg <incal@dataswamp.org> [2022-10-26 15:55]:
> Jean Louis wrote:
> 
> >> I would like to test whether a list contains at least one
> >> non-nil element? If I do that, then I would be able to
> >> continue a loop where a non-nil element would mean that
> >> a match was found.
> >
> > Here is the test for non nil element:
> >
> > (elt (delq nil (list nil nil)) 0) ⇒ nil
> >
> > (elt (delq nil (list nil 1)) 0) ⇒ 1
> 
> Interesting question ...
> 
> (cl-position-if (lambda (e) e) '(nil nil)) ; nil
> (cl-position-if (lambda (e) e) '(nil 1))   ; 1

While `remq' is more suitable as not destructive one:

(elt (remq nil (list nil nil)) 0) ⇒ nil
(elt (remq nil (list nil "any")) 0) ⇒ "any"

cl- is Common Lisp prefix to conform those people who are used to
Common Lisp.  Those functions are bloated.

(defun list-has-non-nil-p (list)
  "Test if list has non nil element."
  (elt (remq nil list) 0))

(list-has-non-nil-p '(1 2 3)) ⇒ 1

(list-has-non-nil-p '(nil nil nil)) ⇒ nil



-- 
Jean

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