For loop in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a for loop in Rust?

A for loop in Rust is a control flow statement that repeats a block of code for each item in a collection or range.

beginner

How do you write a for loop to print numbers 1 to 5 in Rust?

You use a range with the syntax:

for i in 1..=5 {
    println!("{}", i);
}

This prints numbers from 1 to 5 inclusive.

beginner

What does the range 1..5 mean in a Rust for loop?

The range 1..5 means numbers from 1 up to but not including 5, so it includes 1, 2, 3, and 4.

intermediate

Can you use a for loop to iterate over elements in a vector in Rust?

Yes, you can loop over a vector like this: <pre>let v = vec![10, 20, 30];
for val in &v {
    println!("{}", val);
}</pre> This prints each element in the vector.

beginner

What happens if you use for i in 0..=3 in Rust?

The loop runs with i = 0, 1, 2, 3 because ..= means inclusive range including the last number.

What does the Rust for loop for i in 1..4 do?

A Loops with i = 1, 2, 3

B Loops with i = 1, 2, 3, 4

C Loops with i = 0, 1, 2, 3

D Loops with i = 4 only

The range 1..4 includes 1, 2, and 3 but excludes 4.

How do you loop over all elements in a vector v in Rust?

A for val in v { ... }

B for val in &v { ... }

C for val in v[] { ... }

D for val in v() { ... }

Using &v borrows the vector and lets you iterate over its elements safely.

What symbol is used for an inclusive range in Rust?

A ..=

B ...

C ..

D =>

The inclusive range uses ..= to include the last number.

Which of these is a valid for loop in Rust?

A for i = 0 to 5 { println!("{}", i); }

B for (i=0; i<5; i++) { println!("{}", i); }

C for i in 0..5 { println!("{}", i); }

D loop i in 0..5 { println!("{}", i); }

Rust uses for i in range syntax, not C-style for loops.

What will this code print?

for x in 3..=5 {
    println!("{}", x);
}

A 5 only

B 3 4

C 4 5

D 3 4 5

The inclusive range 3..=5 includes 3, 4, and 5.

Explain how a for loop works in Rust and give an example using a range.

Think about how you count numbers one by one.

Describe how to loop over elements in a vector in Rust and why borrowing is important.

Remember Rust’s ownership rules.