Julia set: Difference between revisions

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+=={{header|Emacs Lisp}}==
+<lang lisp>; === Graphical Julia set display in Emacs =====================
+(setq julia-size (cons 300 200))
+(setq xmin -1.5)
+(setq xmax 1.5)
+(setq ymin -1)
+(setq ymax 1)
+(setq julia0 (cons -0.512511498387847167 0.521295573094847167))
+(setq max-iter 100)
+(defun julia-iter-point (x y)
+  "Run the actual iteration for each point."
+  (let ((xp x)
+        (yp y)
+        (it 0)
+        (xt 0))
+    (while (and (< (+ (* xp xp) (* yp yp)) 4) (< it max-iter))
+      (setq xt (+ (* xp xp) (* -1 yp yp) (car julia0)))
+      (setq yp (+ (* 2 xp yp) (cdr julia0)))
+      (setq xp xt)
+      (setq it (1+ it)))
+    it))
+(defun julia-iter (p)
+  "Return string for point based on whether inside/outside the set."
+  (let ((it (julia-iter-point (car p) (cdr p))))
+    (if (= it max-iter) "*" (if (cl-oddp it) "+" "-"))))
+(defun julia-pos (x y)
+  "Convert screen coordinates to input coordinates."
+  (let ((xp (+ xmin (* (- xmax xmin) (/ (float x) (car julia-size)))))
+        (yp (+ ymin (* (- ymax ymin) (/ (float y) (cdr julia-size))))))
+       (cons xp yp)))
+(defun string-to-image (str)
+  "Convert image data string to XPM image with three colors."
+  (create-image (concat (format "/* XPM */
+static char * julia[] = {
+\"%i %i 3 1\",
+\"+      c #ff0000\",
+\"-      c #0000ff\",
+\"*      c #000000\"," (car julia-size) (cdr julia-size))
+    str "};") 'xpm t))
+(defun julia-pic ()
+  "Plot the Julia set in color."
+  (setq all "")
+  (dotimes (y (cdr julia-size))
+    (setq line "")
+    (dotimes (x (car julia-size))
+      (setq line (concat line (julia-iter (julia-pos x y)))))
+    (setq all (concat all "\"" line "\",\n")))
+  (insert-image (string-to-image all)))
+(julia-pic)</lang>
 =={{header|F_Sharp|F#}}==