xlisponly/lsp/dragon.lsp

   1 ;; DRAGON.L FOR PC-LISP V2.10
   2 ;; Modified for xlisp 2.1d (w. graphics extensions) by Tom Almy
   3 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~
   4 ;;     Draw an Nth order Dragon Curve requires Turtle.l routines to run.
   5 ;; Taken From Byte April 1986. Try (DragonCurve 16) then put on supper,
   6 ;; watch the news and come back in an hour and see the results. It takes
   7 ;; about 1/2 hour on my machine so on a normal IBM-PC it should take about
   8 ;; an 1.5 hours.
   9 ;;
  10 ;;              Peter Ashwood-Smith.
  11 ;;              April 1986
  12 ;;
  13 ;;              P.S - This dragon is nicknamed "spot"
  14
  15 #-:turtle (load "turtle")
  16
  17 (defvar *StepSize* 1)
  18
  19 (defun Dragon(sign level)
  20        (if    (zerop level)
  21               (TurtleForward *StepSize*)
  22               (progn
  23                 (setq level (1- level))
  24                 (TurtleRight (* 45 sign))
  25                 (Dragon -1 level)
  26                 (TurtleLeft (* 90 sign))
  27                 (Dragon 1 level)
  28                 (TurtleRight (* 45 sign))
  29               )
  30        )
  31 )
  32
  33 (defun DragonCurve (n m)
  34        (setq *StepSize* m)                   ; *StepSize* is global variable
  35        (TurtleGraphicsUp)
  36        (TurtleCenter)
  37        (TurtleGoto 50 50)
  38        (TurtleRight 30)                          ; angle the serpent a bit
  39        (Dragon 1 n)
  40        (gc)
  41 )
  42
  43 (print "Try (DragonCurve 14 1)")