topic Re: Removing elements from a nested list in Visual LISP, AutoLISP and General Customization Forum

Removing elements from a nested list

Browning_Zed — Sat, 31 Jul 2021 14:09:46 GMT

Hi.
What way is there to remove certain elements from lists included in a nested list?
If the original list is like this:
'((1 2 3 4) (1 2 3 4) (1 2 3 4))
how to remove elements (nth 1) and (nth 2) from the list to transform it:
'((1 4) (1 4) (1 4))

Re: Removing elements from a nested list

hak_vz — Sat, 31 Jul 2021 14:51:22 GMT

Try this

(defun rem_nth (lst ntlst / a i ret) (foreach e lst (setq i -1) (while (< (setq i (1+ i)) (length e)) (if (not(member i ntlst)) (setq a (cons (nth i e) a))) ) (setq ret (cons (reverse a) ret) a nil) ) (reverse ret) )

Example (setq mm '((1 2 3 4) (5 6 7 8 ) (9 10 11 12))) (rem_nth mm '(0 1)) ;-->((3 4) (7 8 ) (11 12))

Example 2: Command: (setq mm '((1 2 3 4) (5 6) (9 10 12))) ((1 2 3 4) (5 6) (9 10 12)) Command: (rem_nth mm '(3 4)) ((1 2 3) (5 6) (9 10 12))

Re: Removing elements from a nested list

pbejse — Mon, 02 Aug 2021 16:28:34 GMT

Another

(defun _remover (l o) (if l (cons (repeat (setq i (length (car l))) (if (not (vl-position (setq i (1- i)) o)) (setq nl (cons (nth i (car l)) nl)) ) nl ) (_remover (cdr l) (progn (setq nl nil) o)) ) ) )

(defun _remove (lst n / a i nl l) (while (setq a (car lst)) (setq nl nil lst (Cdr lst)) (repeat (setq i (length a)) (if (not (vl-position (setq i (1- i)) n)) (setq nl (cons (nth i a) nl)) ) ) (setq l (cons nl l)) ) (reverse l) )

HTH

Re: Removing elements from a nested list

ronjonp — Mon, 02 Aug 2021 20:57:32 GMT

Based on your example lists are you wanting to remove duplicate entries ?

(setq l '((1 2 3 4) (1 2 3 4) (1 2 3 4))) (cons (car l) (vl-remove (car l) l))

This too.