Rust If/Else, Loop, While, and For

If Expressions

In Rust, if is an expression, not just a statement — it can return a value:

let number = 7;

if number < 5 {
    println!("Small");
} else if number < 10 {
    println!("Medium");
} else {
    println!("Large");
}

// if as expression
let category = if number < 5 { "small" } else { "large" };
println!("{}", category);

Loop — infinite loop

let mut counter = 0;
let result = loop {
    counter += 1;
    if counter == 10 {
        break counter * 2; // loop returns a value!
    }
};
println!("Result: {}", result); // 20

While loop

let mut n = 1;
while n < 100 {
    n *= 2;
}
println!("{}", n); // 128

For loop

// Iterate over a range
for i in 0..5 {
    println!("{}", i); // 0, 1, 2, 3, 4
}

// Inclusive range
for i in 1..=5 {
    println!("{}", i); // 1, 2, 3, 4, 5
}

// Iterate over a collection
let arr = [10, 20, 30, 40, 50];
for element in arr {
    println!("{}", element);
}

Match — powerful pattern matching

let coin = "quarter";
let value = match coin {
    "penny"   => 1,
    "nickel"  => 5,
    "dime"    => 10,
    "quarter" => 25,
    _         => 0, // catch-all pattern
};
println!("{} cents", value); // 25 cents