topic Re: vl-sort a list of lists in Visual LISP, AutoLISP and General Customization Forum

vl-sort a list of lists

dvertz — Sun, 13 Apr 2025 19:07:53 GMT

I have a list of lists I would like to sort by two entries. I once had a need to do a sort and the forum helped a lot. So, I thought I would ask again. I thought I would first attempt the code I was once given and as I was studying how it worked and how I could use it, I found that vl-sort will remove duplicate items. And then someone posted code in CADTutor that Kent1Cooper had wrote using mapcar to retain the duplicates. His code is slightly above my abilities.

My list is:

(setq LST
'(((1 . "T1") (2 . "l-cre-non.dwg") (3 . 4) (4 . "CREPE MYRTLE") (5 . 8) (6 . 1))
((1 . "T2") (2 . "l-mag-non.dwg") (3 . 12) (4 . "MAGNOLIA") (5 . 24) (6 . 1))
((1 . "T3") (2 . "l-oak-non.dwg") (3 . 10) (4 . "OAK") (5 . 20) (6 . 1))
((1 . "T4") (2 . "l-app-non.dwg") (3 . 12) (4 . "APPLE") (5 . 24) (6 . 1))
((1 . "T5") (2 . "l-app-non.dwg") (3 . 8) (4 . "APPLE") (5 . 16) (6 . 2))
))

I would like to first sort by association 4 (cdr (assoc 4 LST)), then by association 3 (cdr (assoc 3 LST))

The list should be returned as:

(setq LST
'(((1 . "T5") (2 . "l-app-non.dwg") (3 . 8) (4 . "APPLE") (5 . 16) (6 . 2))
((1 . "T4") (2 . "l-app-non.dwg") (3 . 12) (4 . "APPLE") (5 . 24) (6 . 1))
((1 . "T1") (2 . "l-cre-non.dwg") (3 . 4) (4 . "CREPE MYRTLE") (5 . 8) (6 . 1))
((1 . "T2") (2 . "l-mag-non.dwg") (3 . 12) (4 . "MAGNOLIA") (5 . 24) (6 . 1))
((1 . "T3") (2 . "l-oak-non.dwg") (3 . 10) (4 . "OAK") (5 . 20) (6 . 1))
))

I would appreciate any help given. Thanks.

Re: vl-sort a list of lists

ВeekeeCZ — Sun, 13 Apr 2025 19:41:46 GMT

Try these. It shouldn't remove any items.

(setq lst (vl-sort lst '(lambda (e1 e2) (< (cdr (nth 2 e1)) (cdr (nth 2 e2))))))

(setq lst (vl-sort lst '(lambda (e1 e2) (< (cdr (nth 3 e1)) (cdr (nth 3 e2))))))

or you can use your assoc as well

(setq lst (vl-sort lst '(lambda (e1 e2) (< (cdr (assoc 3 e1)) (cdr (assoc 3 e2))))))

(setq lst (vl-sort lst '(lambda (e1 e2) (< (cdr (assoc 4 e1)) (cdr (assoc 4 e2))))))

Re: vl-sort a list of lists

Kent1Cooper — Sun, 13 Apr 2025 19:44:08 GMT

I would take a look, but so I don't have to start from scratch, post a link to the Cadtutor place with the code, or the code itself if it's not too long. [I don't participate there, but I'm happy to see things spread around. Whoever posted it must have gotten it from here somewhere -- a link to that somewhere would also suffice, if that's how they posted it.]

Re: vl-sort a list of lists

dvertz — Mon, 14 Apr 2025 12:05:01 GMT

BeekeeCZ,

Thank you so much, I did not think it would be that simple. That is code I can actually understand (mostly). I thought that code would remove the duplicate "Apple".

Kent1Cooper,

Thanks for the reply. BeekeeCZ appears to have the solution. I have only ran one test, so I'll need to run more to be sure. But currently it seems where I had worked out a bug in my code, another has presented itself in building the list of lists. More debugging to do. But if you would like to look at where you were mention (yes. they said it was from the Autodesk forums), here is the link: https://www.cadtutor.net/forum/topic/78029-vl-sort-kinda-sucks/

Re: vl-sort a list of lists

MunteanStefan — Mon, 14 Apr 2025 13:21:40 GMT

vl-sort removes duplicates only in lists of integers.

For your sample, you can use this:

(vl-sort lst '(lambda (a b) (if (eq (cdr (assoc 4 a)) (cdr (assoc 4 b))) (< (cdr (assoc 3 a)) (cdr (assoc 3 b))) (< (cdr (assoc 4 a)) (cdr (assoc 4 b))) ) ) )

Re: vl-sort a list of lists

dvertz — Mon, 14 Apr 2025 13:31:13 GMT

MunteanStefan,

Thanks for that info. I will keep that in mind next time I attempt using vl-sort.

Re: vl-sort a list of lists

Sea-Haven — Tue, 15 Apr 2025 00:22:41 GMT

Just a comment do you really need the list to be a dotted pair ? Why not just a plain list, each item can still be found using nth x lst) and sort on (nth 3 lst)

(1 . "T5") (2 . "l-app-non.dwg") (3 . 8) (4 . "APPLE") (5 . 16) (6 . 2)) ("T5" "l-app-non.dwg" 8 "APPLE" 16 2)

(setq LST '( ("T1" "l-cre-non.dwg" 4 "CREPE MYRTLE" 8 1) ("T2" "l-mag-non.dwg" 12 "MAGNOLIA" 24 1) ("T3" "l-oak-non.dwg" 10 "OAK" 20 1) ("T4" "l-app-non.dwg" 12 "APPLE" 24 1) ("T5" "l-app-non.dwg" 8 "APPLE" 16 2) ) ) ; sorts on two items (setq lst (vl-sort lst '(lambda (a b) (cond ((< (nth 3 a) (nth 3 b))) ((= (nth 3 a) (nth 3 b)) (< (nth 4 a) (nth 4 b))) ) ) ))