aUCBLogo Demos and Tests / testphaselocking

to testphaselocking
;lockit stop
   setUpdateGraph "false
   forever
    [   clearScreen
      ;pr repcount
      catch "error [ignore runResult [lockit]]
      err=Error
      if :err != []
      [   clearText
         print :err.2
         for [k 1 100]
         [   waitms 10
            dispatchmessages
         ]
      ]
      updategraph
      updateVars
      dispatchMessages
      if Key? [stop]
   ]
end

to lockit
   imax=100
   f=10
   t=rseq 0 f imax
   x=rseq -400 400 imax
   Ur=(sin t*360+random 360)*100+rnd*10
   clearScreen
   setpc 0
   pu setx -400 pd
   setXY x Ur
   i=2
   while [i<imax]
   [
      while [Ur.i>=0 and2 i<imax]
      [   i=i+1
      ]
      while [Ur.i<=Ur.(i-1) and2 i<imax]
      [   i=i+1
      ]
      while [Ur.i<0 and2 i<imax]
      [   i=i+1
      ]
      i1=i-1
      while [Ur.i<=0 and2 i<imax]
      [   i=i+1
      ]
      i2=i+1
      if i2 > imax [break]
      ifelse Ur.i2 != Ur.i1
      [   r=abs Ur.i1/(Ur.i2-Ur.i1)
      ][   r=0.5
      ]
      im=i1+(i2-i1)*r
      izero=mod im f
      xm=im/imax*800-400
      xzero=izero/imax*800-400
      setpc 1
      pu   setxy x.i1 -200 pd
      setXY x.i1 200
      setpc 2
      pu   setxy x.i2 -200 pd
      setXY x.i2 200
      setpc 4
      pu   setxy xm -200 pd
      setXY xm 200
      setpc HSBA 300 1 0.5 0.2
      pu   setxy xzero -200 pd
      setXY xzero 200
      i=i+1
   ]
   updateGraph
   for [k 1 100]
   [   waitms 10
      dispatchmessages
   ]
end