Category : Miscellaneous Language Source Code
Archive   : PCLISP30.ZIP
Filename : TURTLE.L

;; TURTLE.L for PC-LISP.EXE V2.13
;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
;; A set of rough turtle graphics primitives to demonstrate PC-LISP's BIOS
;; graphics routines. These routines are pretty self explanitory. The first
;; 5 defun's define the primitives, next are a set of routines to draw things
;; like squares, triangles etc. Try the function (GraphicsDemo). It will
;; draw Squirals, Trianglerals, etc. Note that the BIOS line drawing is really
;; slow. This is because the BIOS 'set dot/pixel' routine is used for every
;; point in a line. Using the BIOS has the advantage however of portability,
;; these routines work on virtually every MS-DOS machine. The global variable
;; !Mode controls the graphics resolution that will be used. It is set by
;; default to 6, I set it to 8 or 9 for my Tandy 2000. You can adjust the code
;; to support your machines higher resolution modes. More 640x400 modes can be
;; supported by (= !Mode NN) at ### PATCH POINT 1 ### where NN is the value
;; to pass to (#srcmde#) Ie the value to pass in AH when INT 10H is generated
;; with AL=0 (the BIOS Set CRT Mode call). If your machines has high resolution
;; modes besides the 640x400 say X * Y resolution associated with mode NN then
;; add the following code at ### PATCH POINT 2 ### (where AA is X/2, BB is Y/2
;; CC is the ratio X/Y and DD is the number of pixels that should correspond
;; to one Turtle movement Unit):
;;
;; ((= !Mode NN)
;; (setq CenterX AA CenterY BB Scale CC Lfactor DD)
;; (TurtleCenter))
;;
;; Peter Ashwood-Smith
;; August 22nd, 1986
;;

(setq !Mode 6) ; default setting

(defun TurtleGraphicsUp()
(#scrmde# !Mode)(#scrsap# 0)
(cond ((= !Mode 6) ; 640x200 B&W mode
(setq CenterX 100 CenterY 100 Scale 3.2 Lfactor 1)
(TurtleCenter))
;
((= !Mode 7)
(patom '|mode 7 not allowed|))
;
((or (= !Mode 8) (= !Mode 9) ; Tandy 2000 640x400
(= !Mode 64) ; AT&T 6300 640x400?
; ### PATCH POINT 1 ###
)
(setq CenterX 266 CenterY 200 Scale 1.2 Lfactor 2)
(TurtleCenter))
;
; ### PATCH POINT 2
;
(t (patom '|unsupported mode|))
)
)

(defun TurtleGraphicsDown()
(#scrmde# 2))

(defun TurtleCenter()
(setq Lastx CenterX Lasty CenterY Heading 1.570796372))

(defun TurtleRight(n)
(setq Heading (plus Heading (times n 0.01745329))))

(defun TurtleLeft(n)
(setq Heading (diff Heading (times n 0.01745329))))

(defun TurtleGoTo(x y)
(setq Lastx (quotient x Scale) Lasty (times y Lfactor) ))

(defun TurtleForward(n)
(setq n (times n Lfactor)
Newx (plus Lastx(times(cos Heading)n))
Newy (plus Lasty(times(sin Heading)n)))
(#scrline# (times Lastx Scale) Lasty (times Newx Scale) Newy 1)
(setq Lastx Newx Lasty Newy)
)

;
; end of Turtle Graphics primitives, start of Graphics demonstration code
; you can cut this out if you like and leave the Turtle primitives intact.
;

(defun Line_T(n)
(TurtleForward n) (TurtleRight 180)
(TurtleForward (quotient n 4))
)

(defun Square(n)
(TurtleForward n) (TurtleRight 90)
(TurtleForward n) (TurtleRight 90)
(TurtleForward n) (TurtleRight 90)
(TurtleForward n)
)

(defun Triangle(n)
(TurtleForward n) (TurtleRight 120)
(TurtleForward n) (TurtleRight 120)
(TurtleForward n)
)

(defun Make(ObjectFunc Size times skew)
(prog()
TOP:(cond ((zerop times) (return)))
(ObjectFunc Size)
(TurtleRight skew)
(setq times (1- times))
(go TOP:)
)
)

(defun GraphicsDemo()
(TurtleGraphicsUp)
(Make Square 40 18 5) (Make Square 60 18 5)
(gc) ; idle work
(TurtleGraphicsUp)

(Make Triangle 40 18 5) (Make Triangle 60 18 5)
(gc) ; idle work
(TurtleGraphicsUp)
(Make Line_T 80 50 10)
(gc) ; idle work
(TurtleGraphicsDown)
)