Re: Understanding dotimes skipping by 2

[Tim Johnson]

* Van L <van@scratch.space> [180927 17:39]:
> 
> > the following code snippet is as follows:
> > (setq l `(1 2 3 4 5 6 7 8 9 0))
> > (1 2 3 4 5 6 7 8 9 0)
> > ;; iterate through a list two elements at a time
> > (let ((x 0))
> >  (dotimes (/ (length l) 2)
> >    (progn
> >      (insert (format "%s %s, " (nth x l) (nth (+ x 1) l)))
> >      (setq x (+ x 2)))))
> > 
> > ;; and below are the results
> > 1 2, 3 4, 5 6, 7 8, 9 0, nil nil, nil nil, nil nil, nil nil, nil nil, 2
> > 
> > I'm confused about the output (nil etc...)which follow the expected 
> > numbers. 
> > could someone explain?
> 
> The first argument to dotimes needs a symbol to value binding at a guess.
> 
> The character l and 1 are too easy to confuse in reading you might want to 
> avoid that.
> 
> (setq q '(1 2 3 4 5 6 7 8 9 0))
> (let ((x 0))
>   (dotimes (i (/ (length q) 2))
>     (progn
>       (insert (format "%s %s, " (nth x q) (nth (+ x 1) q)))
>       (setq x (+ x 2)))))
> 
> ; 1 2, 3 4, 5 6, 7 8, 9 0, 
  Good practices tip. Thanks Van ..
-- 
Tim Johnson
http://www.tj49.com