While Loop

A for loop runs once for every number in a range. A while loop keeps running as long as a condition is true:

var count := 3
while count > 0:
	print(count)
	count -= 1
print("Go!")

3
2
1
Go!

The condition is checked before every iteration. When count becomes 0, count > 0 is false, so the loop stops and the program continues after it. If the condition is false from the start, the block never runs.

The block must change something the condition depends on. Here count -= 1 brings count closer to 0. Without it, the condition would stay true and the loop would never end.

Use while when you do not know in advance how many iterations you need. For example, this finds the smallest power of 2 that is greater than 27:

var number := 27
var power_of_two := 1
while power_of_two <= number:
	power_of_two *= 2
print(power_of_two)

power_of_two doubles on each iteration: 2, 4, 8, 16, 32. At 32, power_of_two <= number is false, so the program prints 32.