TestTree

{ This program defines several subroutines.
  It does not produce any picture when it
  is run.  After it is run, use the
  command "testTree" in the xTurtle applet's
  text-input box. }



SUB Tree(size, complexity)

 { This recursive subroutine (from Figure 7.8
   of "The Most Complex Machine") draws a 
   binary tree.  The height of the tree
   is given, approximately, by the parameter
   "size"; the number of levels of branching
   is given by the parameter "complexity."
   After the tree is drawn, the turtle is left
   at its original position and heading. }

   IF complexity = 0 THEN
      forward(size)
      back(size)
   ELSE 
      forward(size/2)
      turn(45)
      Tree(size/2, complexity - 1)
      turn(-90)
      Tree(size/2, complexity - 1)
      turn(45)
      back(size/2)
   END IF

END SUB



SUB TestTree
 
 { This subroutine can be called to draw
   sample trees.  The user is asked to
   specify the complexity. }

   DECLARE complexity

   AskUser("What level of complexity do you want (0 to 12)?", complexity)

   { Adjust the complexity to a reasonable value. }
   complexity := trunc(complexity)
   IF complexity < 0 THEN
      complexity := 0
      TellUser("Using complexity = 0.")
   END IF
   IF complexity > 12 THEN
      complexity := 12
      TellUser("Using complexity = 12.")
   END IF

   penUp        { Move to starting position. }
   MoveTo(0,-9)
   penDown
   face(90)
   clear

   Tree(18,complexity)  { Draw the tree. }

END SUB