Removing lists from list based on length

[Stan]

The following does almost what I want. How do I get it to generate the same output without the nils? Thanks,

Stan

(setq modes '((a b c) (d e f) (g h) (i j) (k) (l m n)))

(defun xnotemodes (x) (if (= (length x) 3) x ))

(mapcar #'xnotemodes modes)

--> ((a b c) (d e f) nil nil nil (l m n))

Here are two things I tried which did not work:

(setq modes '((a b c) (d e f) (g h) (i j) (k) (l m n)))

(defun xnotemodes (x) (remove-if (= (length x) 3) x ))  

(mapcar #'xnotemodes modes)

--> ERROR: Undefined function t called with arguments (a).

(setq modes '((a b c) (d e f) (g h) (i j) (k) (l m n)))

(defun xnotemodes (x) (remove-if 

                                      (not (equal (length x) 3)) 

                              x))

(mapcar #'xnotemodes modes)

-->ERROR: Undefined function nil called with arguments (a).

[ole]

maybe is misunderstand what you want:

(setq modes '((a b c) (d e f) (g h) (i j) (k) (l m n)))
(defun xnotemodes (x) (if (= (length x) 3) x ))

(remove 'nil (mapcar #'xnotemodes modes))
--> ((a b c) (d e f) (l m n))


hth

ole

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[pstone imap]

Mapcan skips nils but you need to list x, otherwise it makes flat result.

(setq modes '((a b c) (d e f) (g h) (i j) (k) (l m n)))

(defun xnotemodes (x) (if (= (length x) 3) (list x)))

(mapcan #'xnotemodes modes)

--> ((a b c) (d e f) (l m n))

[Stan]

Ole and Peter--thank you--both helpful solutions.

Stan

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