slides.md

title	Fractals
subtitle	Functions and Recursion in Scratch and Python
revealjs-url	./lib/reveal
theme	fractals
transition	slide

Welcome

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• Welcome to CoderDojoDC
• Welcome to the Maryland STEM Festival

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What are Fractals?

Fractals are shapes with some special characteristics:

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• Fine Structure
• Self-Similarity
• Scaled Symmetry
• Recursion

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Building a Fractal (1)

To make a fractal, start with a basic shape or line

Building a Fractal (2)

You then repeat the same line in each of the parts of the original

Building a Fractal (3)

As you continue to repeat, or recurse downward, the shape becomes more intricate

Programming Fractals

In order to draw fractals with computers we use two things:

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• Functions: Functions are like little recipes
• Recursion: Recursion is when a function "calls" itself

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A Fractal in Scratch

To draw a fractal in Scratch, we can use the following:

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• Pen Tool
• Custom Blocks (functions)
• Recursion (putting a custom block inside itself)

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Let's Try it Out!

A Fractal Project on the Scratch Website

A Fractal in Python

import turtle        # imports the turtle module
t = turtle.Turtle()  # creates a turtle
t.forward(100)       # draws 100 pixels forward
t.left(60)           # turns left 60°
t.forward(100)       # draws 100 pixels forward
t.right(120)         # turns right 120°
t.forward(100)       # draws 100 pixels forward
t.left(60)           # turns left 60°
t.forward(100)       # draws 100 pixels forward
turtle.done()        # keeps the window open

The Best Way to Learn is By Doing

• See if you can change the Scratch project to draw your own shapes
• If you want to try Python, have a look at the examples