Summary

In this lesson, you learned that:

A loop repeats a block of code. Each run of the block is an iteration. Indent the block by 4 spaces.
while condition do … end repeats the block while the condition is true. Something in the block must change, so that the condition becomes false at some point. Otherwise, the loop never ends, and on this site the program is stopped after 5 seconds. What it printed until then stays in the output.
for i = 1, 10 do … end counts from 1 to 10, including both. The loop makes i local by itself, and after the loop's end, i is nil.
A third number is the step: for i = 10, 1, -1 counts down, and for i = 1, 9, 2 takes every other number. If the start is past the end, the loop runs zero times. Watch out for being off by one.
Use for when you know how many times the loop will run, and while when you don't.
A sum: a variable that starts at 0 before the loop, adds each value inside it (total = total + value), and is printed after the loop. The average is the sum divided by the number of values.
Counting: a counter that starts at 0 and goes up by 1 inside an if. day % 5 == 0 picks every 5th day.
repeat … until condition checks the condition after the block, so the block runs at least once, and it stops when the condition is true. The condition can use local variables from the block.
break ends a loop right away. Lua has no continue: put the rest of the block in an if instead.
Loops can be nested: the inner loop runs all the way through in every iteration of the outer one. io.write writes texts and numbers without a new line and without tabs, and an empty print() ends the line.

In the next lesson, you'll learn about tables: a single variable that holds a whole list of values, such as all of Emma's crops. You'll go through them with the loops you know now.

Instructions

Let's practice with Emma's plan for the next 12 days. With a for loop, print one line for each day from 1 to 12. Every 3rd day is for watering, every 4th day for the market, and on a day that is both (here only day 12), Emma does both. On the other days, she weeds. Check “both” first, otherwise day 12 would only be for watering. The program prints:

Day 1: weeding
Day 2: weeding
Day 3: watering
Day 4: market
Day 5: weeding
Day 6: watering
Day 7: weeding
Day 8: market
Day 9: watering
Day 10: weeding
Day 11: weeding
Day 12: watering and market

Emma earns 40 coins on each market day. Before the loop, create a local variable coins with the value 0, and in the loop, add 40 to it on every market day (day 12 too). After the loop, print:

Coins from the market: 120

Emma is saving up for a new barn door that costs 300 coins, and each further market day brings 40 more. At the end of the program, write a while loop that adds 40 to coins while it's less than 300, and counts these market days in a new variable. After the loop, print:

More market days: 5

Start programming for free

10/10