Data commit

Task/Mandelbrot-set/ACL2/mandelbrot-set.acl2

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+(defun abs-sq (z)
+   (+ (expt (realpart z) 2)
+      (expt (imagpart z) 2)))
+
+(defun round-decimal (x places)
+   (/ (floor (* x (expt 10 places)) 1)
+      (expt 10 places)))
+
+(defun round-complex (z places)
+   (complex (round-decimal (realpart z) places)
+            (round-decimal (imagpart z) places)))
+
+(defun mandel-point-r (z c limit)
+   (declare (xargs :measure (nfix limit)))
+   (cond ((zp limit) 0)
+         ((> (abs-sq z) 4) limit)
+         (t (mandel-point-r (+ (round-complex (* z z) 15) c)
+                            c
+                            (1- limit)))))
+
+(defun mandel-point (z iters)
+   (- 5 (floor (mandel-point-r z z iters) (/ iters 5))))
+
+(defun draw-mandel-row (im re cols width iters)
+   (declare (xargs :measure (nfix cols)))
+   (if (zp cols)
+       nil
+       (prog2$ (cw (coerce
+                    (list
+                     (case (mandel-point (complex re im)
+                                         iters)
+                           (5 #\#)
+                           (4 #\*)
+                           (3 #\.)
+                           (2 #\.)
+                           (otherwise #\Space))) 'string))
+               (draw-mandel-row im
+                                (+ re (/ (/ width 3)))
+                                (1- cols)
+                                width iters))))
+
+(defun draw-mandel (im rows width height iters)
+   (if (zp rows)
+       nil
+       (progn$ (draw-mandel-row im -2 width width iters)
+               (cw "~%")
+               (draw-mandel (- im (/ (/ height 2)))
+                            (1- rows)
+                            width
+                            height
+                            iters))))
+
+(defun draw-mandelbrot (width iters)
+   (let ((height (floor (* 1000 width) 3333)))
+        (draw-mandel 1 height width height iters)))