Data commit

Task/Pentagram/Jq/pentagram.jq

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+# Input: {svg, minx, miny, maxx, maxy}
+def svg:
+  # viewBox = <min-x> <min-y> <width> <height>
+  "<svg viewBox='\(.minx - 4|floor) \(.miny - 4 |floor) \(6 + .maxx - .minx|ceil) \(6 + .maxy - .miny|ceil)'",
+  "     preserveAspectRatio='xMinYmin meet'",
+  "     xmlns='http://www.w3.org/2000/svg' >",
+  .svg,
+  "</svg>" ;
+
+# Input: an array of [x,y] points
+def minmax:
+  {minx: (map(.[0])|min),
+   miny: (map(.[1])|min),
+   maxx: (map(.[0])|max),
+   maxy: (map(.[1])|max)} ;
+
+# Input: an array of [x,y] points
+def Polyline($fill; $stroke; $transform):
+  def rnd: 1000*.|round/1000;
+  def linearize: map( map(rnd) | join(" ") ) | join(", ");
+
+  "<polyline points='"
+   + linearize
+   + "'\n style='fill:\($fill); stroke: \($stroke); stroke-width:3;'"
+   + "\n transform='\($transform)' />" ;
+
+# Output: {minx, miny, maxx, maxy, svg}
+def pentagram($dim):
+  (8 * (1|atan)) as $tau
+  | 5 as $sides
+  | [ (0, 2, 4, 1, 3, 0)
+     | [  0.9 * $dim * (($tau * $v / $sides) | cos),
+          0.9 * $dim * (($tau * $v / $sides) | sin) ] ]
+  | minmax
+    + {svg: Polyline("seashell"; "blue"; "rotate(-18)" )} ;
+
+pentagram(200)
+| svg