newlispfanclub.alh.net

Posted: **Thu Oct 15, 2009 1:14 pm**

(define (crawler-tractor )
   (begin (println "Hi for the " (inc counter) ". time. ")
          (push (last crawler-tractor) crawler-tractor -1)
          (when (> (length crawler-tractor) 3) 
                (pop crawler-tractor 1))))

works indefinitely, but

Code: Select all

(define-macro (crawler-tractor )
   (begin (println "Hi for the " (inc counter) ". time. ")
          (push (last crawler-tractor) crawler-tractor -1)
          (when (> (length crawler-tractor) 3) 
                (pop crawler-tractor 1))))

doesn't. Any chance for that? It appears that functions didn't lost lot of speed...

Posted: **Thu Oct 15, 2009 2:50 pm**

You got it! The speed impact turns out to be hardly measurable and I love the tractor-crawler as much as you do. It well may be a unique feature of newLISP.

For the uninitiated:

The tractor-crawler code pattern runs infinite without looping or recursion by means of self-modifying code. Statements get continuously appended to the function and popped of at the beginning. The change necessary was additional stack cleanup in the macro block.

newlispfanclub.alh.net

Crawler Tractor doesn't work indefinitely for macros.

Crawler Tractor doesn't work indefinitely for macros.

Re: Tractor-crawler doesn't work indefinitely for macros.