Moves as functions

Classroom resources

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Students will be able to

• I can make a function for a robot move and call it.
• I can build a routine from calls in order.
• I can explain why making a function alone does not move the robot.

Timing

Predict and Run 7 min · Investigate 8 min · Modify 12 min · Make 15 min · Real robot 3 min (optional)

Before class

A function is a named group of blocks that runs when it is called. Students met functions in micro:bit Foundations (flashHeart); here each function is a move: a few motor blocks that end with robot motor stop. A routine is then a list of calls, which is easy to read and easy to change. The classic slip returns: making a function does nothing until something calls it (Leo's robot).

Functions are in Advanced › Functions (Make a Function…, then a call block appears). Each move should end with robot motor stop, or the next move starts from a moving robot. MOVE Motor classes can build the same moves from the Kitronik blocks with pauses.

Running the lesson

1. Predict: most say twice. A few say nothing (they confuse making with calling): good to hear before Leo's robot.
2. Run: press A on the simulator's micro:bit, not the keyboard.
3. Investigate: Leo's robot is the define-not-call slip from Foundations. Ask: where is spin called?
4. Modify: the call blocks appear in Functions after the function is made.
5. Make: encourage names that describe the move. The check needs three functions (wiggle plus two), A+B, and one move called twice.
6. Real robot (optional): fix a move once and every call in the routine changes.

The hard part (on purpose)

Making a function doesn't move the robot; calling it does. When nothing happens, ask where the call block is.

When students get stuck

Answers to the checks

1. Predict: What happens when you press A?
   It wiggles twice, then stops. Button A calls wiggle two times, and each wiggle turns right, turns left, then stops.
2. Spin once: This version has a second move, spin. How many times does each block inside spin run when you press B once?
   Once
   B calls spin once, so its blocks run once: turn for 1.2 seconds, then stop.
3. Leo's robot: Leo made a spin function. When he presses A, his robot only drives forward. Why?
   Nothing calls spin: button A has drive blocks instead of a call to spin
   Making a function only names the move. Its blocks run when something calls it, and nothing calls spin. Button A needs call spin.

Solutions

One possible solution for each task. Other correct programs are fine.

Modify › A new move

function wiggle () {
    robot.motorTank(50, -50, 300)
    robot.motorTank(-50, 50, 300)
    robot.motorStop()
}
function spin () {
    robot.motorTank(50, -50, 1200)
    robot.motorStop()
}
input.onButtonPressed(Button.A, function () {
    wiggle()
    wiggle()
})
input.onButtonPressed(Button.B, function () {
    spin()
})
robot.elecfreaksCuteBot.start()

Modify › A routine

function wiggle () {
    robot.motorTank(50, -50, 300)
    robot.motorTank(-50, 50, 300)
    robot.motorStop()
}
function spin () {
    robot.motorTank(50, -50, 1200)
    robot.motorStop()
}
input.onButtonPressed(Button.A, function () {
    wiggle()
    spin()
    wiggle()
})
input.onButtonPressed(Button.B, function () {
    spin()
})
robot.elecfreaksCuteBot.start()

Make

function wiggle () {
    robot.motorTank(50, -50, 300)
    robot.motorTank(-50, 50, 300)
    robot.motorStop()
}
function shuffle () {
    robot.motorTank(50, 50, 300)
    robot.motorTank(-50, -50, 300)
    robot.motorStop()
}
function twirl () {
    robot.motorTank(-50, 50, 1200)
    robot.motorStop()
}
input.onButtonPressed(Button.AB, function () {
    shuffle()
    wiggle()
    shuffle()
    twirl()
})
robot.elecfreaksCuteBot.start()

Stretch and support

Stretch: Add robot set color to each move so the lights change with the dance, or play a tone at the start of each move.

Support: Give students the shuffle function made; they make one more move and the A+B routine.

Exit ticket

Why is a dance easier to change when each move is a function?

You change a move in one place, and every call to it in the routine changes too. The routine itself reads as a list of names.

What each step is for

• Investigate: A function is a named move. Making it does nothing on its own; calling it runs the move, as often as you like.
• Modify: Once a move has a name, a routine is just calls in order.

Where it leads

Next unit: Sense. Later, lesson 8 uses radio so one micro:bit can cue several robots to dance together. Class idea: a short robot dance-off, with each group's routine read aloud as a list of move names first.