Add: spirograph.ps

spirograph.ps

@@ -0,0 +1,54 @@
+%!PS
+/R {144} def
+/r {89} def
+/h {55} def
+
+% options
+0.1 setlinewidth
+2 setlinecap
+2 setlinejoin
+
+% set origin on center of page
+/in {72 mul} def
+8.5 in 2 div
+11  in 2 div
+translate
+
+% Position x(t), y(t)
+/x {
+	/t exch def
+	R r sub t cos mul
+	t 1 R r div sub mul cos h mul
+	add
+	% Normalize
+	144 mul R r sub h add div 
+} def
+
+/y {
+	/t exch def
+	R r sub t sin mul
+	t 1 R r div sub mul sin h mul
+	add
+	% Normalize
+	144 mul R r sub h add div 
+} def
+
+% a=mcd{r,R}
+/a {r} def
+/b {R} def
+{
+	b 0 ne exit if
+	/x {a b mod} def
+	/a {b} def
+	/b {x} def
+} loop
+
+% Draw
+0 x 0 y moveto
+0 1 360 r r mul mul a div 
+{
+	dup x exch y lineto
+} for
+
+stroke
+showpage