for + Ranges

Goal of This Episode

Use a for loop together with a range to repeat things, without managing a counter yourself.

Main Text

In the last two episodes we learned loop and while, both of which required managing a counter by hand (count -= 1 and so on). Today we’ll learn an even simpler way — the for loop.

for + a Range

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

What Is 0..5?

0..5 is called a range. It means “starting at 0, up to just before 5.” Note: 5 is not included!

So 0..5 gives the five numbers 0, 1, 2, 3, 4.

You can read for i in 0..5 as: “Let i run from 0 to 4 in order, doing what’s inside the curly braces each time.”

Notice that i here doesn’t need a let — for declares it for you automatically. And i is usable anywhere inside the curly braces {} that follow the for.

Want to Include the End? Use 0..=5

fn main() {
    for i in 0..=5 {
        println!("{}", i);
    }
}

0..=5 has an extra =, meaning “including 5.”

Comparison

while and for Can Use break Too

We learned break inside loop earlier, but it also works in while and for. One thing to note: break only jumps out of a loop — it doesn’t jump out of control structures like if. So in the code below, break exits the for loop, not the if:

fn main() {
    for i in 0..10 {
        if i == 5 {
            println!("Found 5 — stopping here!");
            break;
        }
        println!("{}", i);
    }
}

Running this prints only 0~4; when it hits 5, break exits the loop.

Recap

• for i in 0..5 runs i from 0 to 4 (end excluded); 0..=5 includes 5.
• Compared to while, for doesn’t need manual counter increments or condition checks — more concise and less error-prone.
• break works inside loop, while, and for.