Programming - Creating Functions

This year in our Starter Bot Blocks code we are using "functions" for the first time.

Blocks Functions

What is a Function?

Functions act similar to a variable in that we are using one thing to represent another. However, where a variable typically is used in place of something short, such as a number or equation, a function can take the place of several lines of code.

This can be incredibly useful if there is a section of code we know will be repeated or to break apart our code into chunks for easy editing.

Below is a breakdown of our functions:

Function	Purpose
GAMEPAD_INPUT_STATE	Contains the code related to the arm/wrist presets
GAMEPAD_INPUT_TOGGLE	Contains the code for the claw toggle
GAMEPAD_INPUT_MANUAL	Contains the code for manual control of the arm/wrist
GAMEPAD_INTAKE	Contains the code for running the servo on the intake
STATE_MACHINE	Contains all the preset positions for currentState
SPLIT_STICK_ARCADE_DRIVE	Contains the code for driving the robot
TELEMETRY	Contains the telemetry read out code

How do Functions appear in Blocks?

When using functions, our Blocks program becomes divided into different sections containing separate series of code:

Starter Bot 2024-25 Example Code

So let's say we wanted to change how quickly our robot's arm moves during manual control with the d-pad. With our functions organizing our code in chunks, it's easy to find the values we want to change:

Function for Manual Arm/Wrist control

Without the use of functions our code would end up a little long and clunky:

This is intended as an example only and not actual use!

Creating a new Function in Blocks

If we want to create a new function in our Blocks program, we start by pulling a block from the Functions menu:

Functions menu in Blocks

Next we will replace "do something" with an appropriate name. Maybe in this case we are adding a new function for climbing:

Example function for climbing

Once our function is named it will appear in the "Functions" menu to be added to the main loop or wherever we need it within our code!

New function block

New function added to our main code

All that's left is to add whatever code we'd like to be within this function:

Example of a simple code within our function

The Starter Bot is able to climb the lower rung using the existing example program!

If the block is deleted this will remove the function from the "Functions" menu.

Additional Function Example

By default, the Starter Bot's program only references each function once during our loop. The following is intended to be an additional example for reusing functions throughout a program and as an additional educational resource!

This program can be tested on the Starter Bot or another robot using the same configuration file! Create a new OpMode to begin. Ours is called FunctionsDemo.

If you are using the Starter Bot, make sure the arm is adjusted to not drag while the robot drives autonomously.

Let's say we are working on an autonomous code where we want our robot to drive roughly in a square. Remember that autonomous means this code will move the robot on its own when play is pressed:

Simple program for driving in a square

Next, let's say we need the robot to do something between one of the turns, such as move its arm or open a servo's claw. There's a couple of ways we could approach this without functions:

Full code with claw opening after driving two sides

Already our code is getting a little long so let's move our side motion and turn into a function:

Function containing the code for driving and turning

Now our loop may look like this:

Using functions to drive in a square

When we test our code we may notice our robot isn't exactly driving in a square shape. Thankfully with our function in place we only need to change the needed value in one place:

Code for controlling the robot's turn

This change to the function will be reflected anywhere DRIVE_AND_TURN used.

Give it a try by changing the right motor's power or the timer to refine your square!