Lisp Mindstorms

Zoë Charlton, Mid America Greetings #1

XS Lisp, by Taiichi Yuasa, is a Lisp programming environment for Lego Mindstorms. Unlike LegoLisp or LegoScheme,which run on a PC and send commands to the RCX computer, XS Lisp runs right on the RCX itself.

XS Lisp includes the following features:

• read-eval-print loop
• interactive definition and re-definition of functions
• appropriate error messages with backtraces
• function trace and untrace
• dynamic object allocation and garbage collection
• robustness against program errors and stack/buffer overflow
• terminal interrupts
• truly tail-recursive interpreter
• event/timer waiting and asynchronous event watchers
• interface to RIS devices such as motors, sensors, lights, and sounds

Here's some sample code, from Taiichi's ILC 2003 paper:

(define (forward)
  (motor :a (motor :c :forward))
  (play '((:Re4 . 2) (:Do4 . 1) ...)))

(begin
  (speed :a (speed :c :max-speed))
  (forward)
  (with-watcher
    (((touched? 2)
      (motor :a (motor :c :back))
      (sleep 5)
      (motor (if (= (random 2) 0) :a :c)
	     :forward)
      (sleep 5)
      (forward)))
    (wait-until (pressed?))
    (motor :a (motor :c :off))))

Pete Hopkins blogged some notes from Taiichi's ILC talk back in November of last year.

Posted by jjwiseman at September 15, 2004 08:13 AM