topic Re: lambda in Visual LISP, AutoLISP and General Customization Forum

lambda

scott_bolton — Fri, 23 Oct 2020 09:16:26 GMT

After years of lisping I still haven't got round to using lambda. I have a situation now where I think one would be appropriate. I would normally sort this out with while or foreach or repeat but I'd like to attack this with lambda. I have a list of XYZ points and I would like to create a new list of the difference between the XY and Z of each point with reference to the first point. So:

'((10 10 110) (10 34 3) (56 89 245))

would result in

'((0 0 0) (0 24 -107) (46 79 135))

Could someone very kindly point me in the right direction?

Re: lambda

pbejse — Fri, 23 Oct 2020 09:27:28 GMT

(setq lst '((10 10 110) (10 34 3) (56 89 245))) (mapcar '(lambda (l) (mapcar '- l (Car lst)) ) lst )

HTH

Re: lambda

scott_bolton — Fri, 23 Oct 2020 09:33:43 GMT

Jeez, that easy eh? 😉 Thanks, pbejse. Something for me to work on.

Re: lambda

pbejse — Fri, 23 Oct 2020 10:07:25 GMT

@scott_bolton wrote:

Jeez, that easy eh? 😉 Thanks, pbejse. Something for me to work on.

You are welcome S, I'm sure there's another way to code it using lambda, that's the first thing that pops into my head though .

Cheers

Re: lambda

ВeekeeCZ — Fri, 23 Oct 2020 12:20:00 GMT

@pbejse wrote:
(setq lst '((10 10 110) (10 34 3) (56 89 245))) (mapcar '(lambda (l) (mapcar '- l (Car lst)) ) lst )
HTH

The above algorithm translated to the common functions for better understanding.

(defun :mapcar-alternative (lst-o  / 1st-o idx itm-o itm-n lst-n)
  
  (setq lst-n '()
	1st-o (car lst-o))
  
  (foreach itm-o lst-o
    (setq idx 0
	  itm-n '())
    
    (repeat (min (length itm-o)
		 (length 1st-o))
      (setq itm-n (append itm-n (list (- (nth idx itm-o)
					 (nth idx 1st-o))))
	    idx (1+ idx)))
    
    (setq lst-n (append lst-n (list itm-n))))
  
  lst-n)

btw nice one pBe! 👍

Re: lambda

CodeDing — Fri, 23 Oct 2020 13:24:11 GMT

@scott_bolton ,

This might help you for future reference. It's just a visualization so you can see kind-of what's happening...

(defun Add1 (num / ) (+ num 1)) (setq Add2 (lambda (num) (+ num 2))) (Add1 2) -> returns 3 (Add2 1) -> returns 3

Best,

~DD