Topic: Divide List

[MP]

Michael, could the speed not be improved by adding a simple:

Code: [Select]

(DivideList
           '(1 2 3 4 5 6 7 8 9)
           [color=red](function[/color] (lambda (x) (zerop (rem x 3))))
        )
    )


Significantly:

Code: [Select]

Elapsed milliseconds / relative speed for 16384 iteration(s):

    (_SUBDIVIDE (QUOTE (1 2 3 4 5 6 7 8 ...).....1466 / 1.16 <fastest>
    (DIVIDELIST (QUOTE (1 2 3 4 5 6 7 8 ...).....1700 / 1.00 <slowest> [color=green];; (function (lambda ...)) form[/color]
Still prefer the non quoted form myself.

[Lee Mac]

I only mentioned it 'cause I saw VovKa say a bit about using it in another thread on here...   

[MP]

[VovKa]

someone needs a recursion?

Code: [Select]

(defun test (lst fun)
  (if lst
    ((lambda (rest)
       (if (fun (car lst))
(list (cons (car lst) (car rest)) (cadr rest))
(list (car rest) (cons (car lst) (cadr rest)))
       )
     )
      (test (cdr lst) fun)
    )
    '(nil nil)
  )
)
;;;(test '(1 2 3 4 5 6 7 8 9) (lambda (x) (zerop (rem x 3))))

WARNING!
It is slow...

[Lee Mac]

I'm not sure if I am correct in my thinking, but I always try to limit my use of recursive methods to very small tasks, like, for example (something I got from Gile a think...):

Code: [Select]

(defun lst->pt (lst)
  (if lst
    (cons (list (car lst) (cadr lst) (caddr lst))
          (lst->pt (cdddr lst)))))

As I've heard that recursive methods have a limit that is the stack memory.