Re: qsort optimized for brevity


"Marc Battyani" <Marc.Battyani@xxxxxxxxxxxxxxxxxx> wrote
> <nallen05@xxxxxxxxx> wrote
> > noone said it had to be fast right? ; - )
> >
> > (defun qsort (list &optional 2nd)
> > (if (null list)
> > 2nd
> > (let ((max (eval (cons 'max list))))
>
> The eval will be really slow and the evaluation of max will crash if list is too big.
> You should use (reduce 'max list) instead.
>
> But don't worry it will be slow enough anyway ;-)

In fact I would rewrite it that way:
(note that it's not a quick sort anymore)

(defun qsort (list)
(when list
(let ((max (reduce 'max list)))
(cons max (qsort (remove max list :count 1))))))

(qsort '(1 5 3 2 4 6 8 4 5 6 1 5))
(8 6 6 5 5 5 4 4 3 2 1 1)

Marc


.

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