Looping with For

In the last chapter, you learned how to repeat code with while loops. Now let's learn about for loops — a cleaner way to loop when you know exactly how many times you want to repeat something!

Counting with Ranges

A range tells Rust to count from one number to another. Here's how to print the numbers 0 through 4:

rust

fn main() {

for i in 0..5 {

println!("{}", i);

}

The 0..5 part is called a range. It starts at 0 and goes up to (but not including) 5. So you get: 0, 1, 2, 3, 4.

Notice how much simpler this is compared to a while loop — no mut variable, no manual counting!

Inclusive Ranges

What if you want to include the last number? Use ..= instead of ..:

rust

fn main() {

for i in 1..=5 {

println!("{}", i);

}

This prints 1, 2, 3, 4, 5 — the = sign means "include the end number too!"

Range	Numbers you get
`0..5`	0, 1, 2, 3, 4
`1..=5`	1, 2, 3, 4, 5
`1..4`	1, 2, 3
`1..=4`	1, 2, 3, 4

Skipping Numbers with step_by

Want to count by twos? Or threes? Use .step_by():

rust

fn main() {

for i in (0..10).step_by(2) {

println!("{}", i);

}

This prints 0, 2, 4, 6, 8. Notice the parentheses around the range — they're needed when you call .step_by() on a range.

Looping Over Characters

You can loop through the letters in a string using .chars():

rust

fn main() {

for ch in "hello".chars() {

println!("{}", ch);

}

This prints each character on its own line: h, e, l, l, o.

Looping Over a Vector

A vector is like a list of items. You can loop through it with .iter():

rust

fn main() {

let colors = vec!["red", "green", "blue"];

for color in colors.iter() {

println!("I like {}!", color);

}

Using the Loop Variable

The loop variable (like i or ch) changes each time through the loop. You can use it for all kinds of things:

rust

fn main() {

for i in 1..=3 {

println!("{} times 2 is {}", i, i * 2);

}

Summary

Concept	What it does
`for i in 0..5`	Loop with i = 0, 1, 2, 3, 4
`for i in 1..=5`	Loop with i = 1, 2, 3, 4, 5
`(0..10).step_by(2)`	Loop with i = 0, 2, 4, 6, 8
`"text".chars()`	Loop through each character
`vec.iter()`	Loop through each item in a vector

Now let's practice using for loops!