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Barnsley fern: Difference between revisions
→{{header|EasyLang}}: add Emacs Lisp
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rect 0.3 0.3
.</lang>
=={{header|Emacs Lisp}}==
<lang lisp>; Barnsley fern
(defun make-array (size)
"Create an empty array with size*size elements."
(setq m-array (make-vector size nil))
(dotimes (i size)
(setf (aref m-array i) (make-vector size 0)))
m-array)
(defun barnsley-next (p)
"Return the next Barnsley fern coordinates."
(let ((r (random 100))
(x (car p))
(y (cdr p)))
(cond ((< r 2) (setq nx 0) (setq ny (* 0.16 y)))
((< r 9) (setq nx (- (* 0.2 x) (* 0.26 y)))
(setq ny (+ 1.6 (* 0.23 x) (* 0.22 y))))
((< r 16) (setq nx (+ (* -0.15 x) (* 0.28 y)))
(setq ny (+ 0.44 (* 0.26 x) (* 0.24 y))))
(t (setq nx (+ (* 0.85 x) (* 0.04 y)))
(setq ny (+ 1.6 (* -0.04 x) (* 0.85 y)))))
(cons nx ny)))
(defun barnsley-lines (arr size)
"Turn array into a string for XPM conversion."
(setq all "")
(dotimes (y size)
(setq line "")
(dotimes (x size)
(setq line (concat line (if (= (elt (elt arr y) x) 1) "*" "."))))
(setq all (concat all "\"" line "\",\n")))
all)
(defun barnsley-show (arr size)
"Convert size*size array to XPM image and show it."
(insert-image (create-image (concat (format "/* XPM */
static char * mandel[] = {
\"%i %i 2 1\",
\". c #000000\",
\"* c #00ff00\"," size size)
(barnsley-lines arr size) "};") 'xpm t)))
(defun barnsley (size scale max-iter)
"Plot the Barnsley fern."
(let ((arr (make-array size))
(p (cons 0 0)))
(dotimes (it max-iter)
(setq p (barnsley-next p))
(setq x (round (+ (/ size 2) (* scale (car p)))))
(setq y (round (- size (* scale (cdr p)) 1)))
(setf (elt (elt arr y) x) 1))
(barnsley-show arr size)))
(barnsley 400 35 100000)</lang>
=={{header|F sharp|F#}}==
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