Re: [Sbcl-help] Proper Tail recursion ?

[Frank <fa...@ri...>]

I believe it could be done this way:

(defun pow2 (n &optional (acc 1))
  (cond
    ((> n 0)
     (pow2 (- n 1) (* acc 2)))
    (t
     acc)))


On Mon, 2016-01-25 at 05:26 +0100, Mei...@gm... wrote:
> Hi,
> 
> 
> WARNING! NEWBIE QUESTION AHEAD! WARNING! :)
> 
> Recently I read about proper tail recursion and its
> benefits for recursion depth.
> 
> My questions are:
> Does SBCL supports proper tail recursion ?
> And if yes:
> I wrote a simple recursive function, which calculates
> powers of 2:
> 
>     ( defun pow2
> (n)                                                                  
>                                                                      
>                                                      
>       ( cond (( > n 0 ) ( * 2 ( pow2 ( - n 1 ))))
>         (t 1 )))
> 
> 
> At least it calculates the corrects results. ;)
> Is it possible to recode this function in way, which
> makes it proper tail recursive?
> 
> Thank you very much for any help in advance!
> Best regards,
> Meino
> 
> 
> 
> 
> 
> -------------------------------------------------------------------
> -----------
> Site24x7 APM Insight: Get Deep Visibility into Application
> Performance
> APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month
> Monitor end-to-end web transactions and take corrective actions now
> Troubleshoot faster and improve end-user experience. Signup Now!
> http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140
> _______________________________________________
> Sbcl-help mailing list
> Sbc...@li...
> https://lists.sourceforge.net/lists/listinfo/sbcl-help