I am having two problems with SCALE. 1. I cannot set bounds to anything other than integers. For example: (make-instance 'scale :from 0 :to (* 2 pi) ... gives me an error. 2. I am unable to retrieve the :VARIABLE value In the below, vales of UPPER-THETA and FORE-THETA never seem to be anything but 0, no matter where I slide the scale. I have tested all the drawing an update code, I am stumped! (defun controltest () "Test of a user-controlled robot arm" (with-ltk () (let* ((upper-theta 0) (fore-theta 0) (upper-slider (make-instance 'scale :from 0 :to 7 :length 360 :variable upper-theta)) (fore-slider (make-instance 'scale :from 0 :to 7 :length 360 :variable fore-theta)) (cnvs (make-instance 'canvas :width cnvs-width :height cnvs-height)) (upper (manip:uctk-beam :cen-x 200 :cen-y 200 :b-length 40 :b-width 20 :tk-cnvs cnvs)) (fore (manip:uctk-beam :cen-x 0 :cen-y 40 ; relative to upper :b-length 40 :b-width 20 :tk-cnvs cnvs)) (slp-time 50) #|ms|# ) (labels ((update () (draw upper nil) ; contains FORE, no need to draw separately (geo:set-member-theta upper 2 fore-theta) (geo:set-theta upper upper-theta) (after slp-time #'update))) (geo:add-geo upper fore) ; make FORE a member of UPPER (pack cnvs :fill :both :expand 1) (pack upper-slider :side :bottom) (pack fore-slider :side :bottom) (update)))))