## Sunday, November 24, 2013

### Lesson 39 - King of Polygons

Today it was time to get back into action and actually implement the function for drawing a polygon with an arbitrary number of edges.

We started by recapping how to calculate the vertex angle:

360 / n, where n is the number of vertices

Then we started working on the actual function. After maybe 15 minutes of discussion and typing (5 mins allocated for picking a name as always) we came up with

let polygon k=r k (s [fd 50,rt (360 /k)])

Dead simple for a coder but daunting for a 4-year old. When explained, it's not very complex yet. To draw a polygon with k number of edges, you repeat the following k times:

1. Move forward 50 pixels
2. Turn right (360 / k) degrees
So, it was hard but it paid off. After struggling with the first polygon as in

polygon 6

She got crazy and drew all polygons up to 14 edges. Then they didn't fit into the Turtle Roy display anymore and we had to change her program a bit using the Turtle Roy "editor mode": we added fd 20 and lt 180 to the start so that she can squeeze in a couple more polygons. You can check out the end result here.

She was indeed so enthusiastic about polygons that she gave Mom a lesson too. Together they hacked the program so that it moves only 10 pixels at a time, so that they can draw the King of Polygons: the Hectogon. It looks like a circle, actually.

#### 1 comment:

1. Paid *of > off. Good stuff!