Lesson 24: Functions

Prompt: What's one block you'd like to have in Game Lab? What would it do? What code would it use to work?

Think-Pair-Share: Allow students to explain their blocks to a partner before sharing out their ideas.

As students share their ideas, make sure they have a clear idea of the code that they would use to make the block, reminding them that all of the blocks they have learned this chapter (e.g. velocity, collisions) have been built from blocks that they already knew.

Today, we're going to learn how to create our own blocks so that we decide exactly how they will work. These special blocks are called functions, and they are one of the most powerful parts of programming.

Question of the Day: How can programmers use functions to create their own abstractions?

Transition: Move students into Code Studio where they will learn to create and call functions.

Questions to Consider with Video:

• Think of a time when a function might have helped you write a program.
• What code would go in the definition of the function?
• When would you call the function?
• What would you name it?

Goal:

Key Vocabulary:

• Function - a named bit of programming instructions

Make sure students understand the role of the two steps in using functions, as well as seeing functions as a form of "chunking" or abstraction. The function definition should include all of the code that they want to run, and the name of the function should be a short description of the purpose of the code. The function should be called at each place in the program that the student wants that block of code to run.

Introducing Functions

In these first few levels students are just being shown the syntax of functions and are not asked to write or create their own. It can be useful to explain creating a function as basically “creating a new block” just like another programmer created the “isTouching” or “velocity” blocks that they’ve seen actually contain other more complex code.

Why Use Functions

Level 5a, 5b, and 5c introduce three uses of functions, namely removing repetition in programs, allowing code to quickly be changed at multiple points, and providing organization in code. Students will need to write more of their own functions in these levels.

Level 7: Functions in Context

In these levels, students will use functions to organize code within a simple game. While it is not identical to the side scroller, many of the skills and uses of functions in these levels can and should be used when they complete their side scroller.

Key Vocabulary:

• Function - a named bit of programming instructions

Prompt: Why would we say that functions allow us to "create our own blocks?" Why is this something we'd want to do? Why would a function count as an abstraction?

Discuss: Have students discuss at their table before talking as a class.

Goal: Use this first prompt to review what students learned today. When they create a function they are creating their own block that they can call or use whenever they like. They saw at least two primary motivations for creating functions today including:

• Simplifying code by breaking it into logically named chunks
• Allowing a programmer to think at a higher level by hiding the details or a particular bit of programming instructions
• Avoiding repeated code by making one block you can use multiple times

Students should review the definition of abstraction as "a simple way of representing something complex". Note that a function is an abstraction because it allows you to create one simple name for a more complex block of code.

Functions are a useful tool for helping us write and organize more complex pieces of code. As we start looking to the end of the unit and your final project, being able to keep your code organized will be an important skill.

Question of the Day: How can programmers use functions to create their own abstractions?