Project: ask and drive

Plan, build and test one program that asks, drives a square, plays notes and reports.

F1.10Programming basicsGCSE25 min

Time to put the module together. You will build one program, a piece at a time, that asks the user two questions, drives a square from the answers, plays a note at every corner and reports on what it did. Every idea from F1 is in it: sequence, output, calling functions, variables and constants, input, casting and arithmetic.

The brief

The robot asks how long each side of a square should be, in centimetres, and which note to play, in hertz. It drives the square, playing the note for a fifth of a second at each corner, and ends where it started. Then it prints the perimeter and the area of the square it drove.

Plan before you type

Programmers plan a program by its inputs, what it does with them, and its outputs. Fill this in on paper first:

Which data type should each input be? The side could be 12.5 cm, so a float. A note is a whole number of hertz, so an integer.

Step 1: ask and convert

Start with the questions, and print the answers to check them. Checking each step before writing the next is how you catch mistakes while they are small.

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

side = float(input("How long is each side, in cm? "))
note = int(input("Which note, in hertz? "))
print("side", side, "note", note)

Run this in the simulator

Try 20 and 440. Then try 20.5 and 440: the float copes. What happens with 440.5 for the note, and why?

Step 2: one side and one corner

Add one drive and one note, and run it:

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

SPEED = 50

side = float(input("How long is each side, in cm? "))
note = int(input("Which note, in hertz? "))

forward(SPEED, distance=side)
tone(note, 0.2)

Run this in the simulator

SPEED is a constant: every drive will use it, so it lives in one place at the top.

Step 3: the whole square

BugBot can drive in any direction without turning, so a square is forward, right, backward, left. Copy step 2 into the task below and build the other three sides and corners. When the robot draws a square and ends where it started, add the report.

Step 4: the report

Work the perimeter and area out from side with operators. Do not type the answers in: the program has to be right for any side the user gives.

Testing

Run your program with several answers and check each one against what you worked out by hand:

The task types in 25 and 523, the first row.

Task: ask and drive

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

SPEED = 50

# ask the two questions and convert the answers

# drive the square, a note at each corner

# print the perimeter and the area

Challenges

1. Ask for the speed as well, as a third input.
2. Make the robot play a different note at each corner: the note, then a note twice as high, then back.
3. Drive a rectangle instead: ask for the width and the length, and report its perimeter and area.