Ken Tilton wrote:

> Mirko.Vukovic@gmail.com wrote:
> > Hi,
> >
> > I am still in a bit of shock that my first loop attempt works, with
> > one legalistic exception.
> >
> > This is my simple code to show duplicates in a list:
> >
> > (defun show-duplicates (list)
> > (loop
> > initially with ref = (first list)
>
> That is a blank initially clause. CLisp is being nice and coping with
> that and pretending you just wrote (loop with ref = (first list)....
>
> > for entry in (rest list) do
> > (if (equal ref entry)
> > (print entry))
>
> Using when when when is suitable makes code more readable.
>
> > (setf ref entry)))
>
> Loop is pretty powerful so you should have a nervous feeling when you
> find yourself setfing key iteration variables.
>
> It looks as if you are assuming a sorted list and simply printing out
> elements the same as the preceding element:
>
> (loop for (a b) on list
> when (eql a b)
> do (print b))
>
> You get an extra iteration on the last element and nil so an input list
> of '(nil nil) would print an extra duplicate. If that is a problem you can:
>
> (loop for a in list
> for b in (cdr list) ; this will run out first and halt the loop
> when (eql a b)
> do (print b))

(setq list '(0 0 0 2 3 4 4 5 6 6 6))

(loop for a in list
for b in (cdr list) ; this will run out first and halt the loop
when (eql a b)
do (print b))

0
0 4
6 6

newLISP

(setq lst '(0 0 0 2 3 4 4 5 6 6 6))

(apply (fn (a b)(if (= a b) (println a)) b) lst 2)

0
0 4
6 6