While loop in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a while loop in Rust?

A while loop in Rust repeats a block of code as long as a given condition is true. It checks the condition before each repetition.

beginner

How do you write a basic while loop that counts from 1 to 5 in Rust?

You can write it like this:<br><pre>let mut count = 1;
while count <= 5 {
    println!("{}", count);
    count += 1;
}</pre>

beginner

What happens if the condition in a while loop is initially false?

The code inside the while loop will not run at all because the condition is checked before the loop starts.

intermediate

How can you stop an infinite while loop in Rust?

You can stop it by using a break statement inside the loop when a certain condition is met.

beginner

Why do you need to declare the loop variable as mut in a while loop?

Because the variable changes its value inside the loop, it must be mutable (mut) so Rust allows updating it.

What keyword starts a while loop in Rust?

A repeat

B while

C for

D loop

The keyword while is used to start a while loop in Rust.

What happens if the while loop condition is false at the start?

A The loop does not run at all

B The loop runs once

C The loop runs infinitely

D The program crashes

The while loop checks the condition before running. If false, it skips the loop.

How do you stop a while loop early inside the loop?

A exit

B continue

C stop

D break

The break keyword stops the loop immediately.

Why must the loop counter be declared with mut?

A Because it changes value inside the loop

B Because Rust requires all variables to be mutable

C Because it is a constant

D Because it is a string

The counter changes each time the loop runs, so it must be mutable.

Which of these is a correct while loop condition to count from 1 to 3?

A while count == 3

B while count < 3

C while count <= 3

D while count > 3

Using while count <= 3 counts 1, 2, and 3.

Explain how a while loop works in Rust and give a simple example.

Think about counting numbers using a variable that changes.

Describe how to stop an infinite while loop in Rust.

Imagine you want to stop the loop when a number reaches 10.