Logical Operators

Goal of This Episode

Learn to combine multiple conditions with && (and), || (or), and ! (not).

Main Text

Over the last few episodes we learned if, but our conditions were all simple — just one at a time. In real life, you often need to consider several conditions at once, such as “at least 18 years old and a student.” That’s where logical operators come in.

&& — AND

Both conditions must hold for the result to be true:

fn main() {
    let age = 24;
    let is_student = true;

    if age >= 18 && is_student {
        println!("An adult student");
    }
}

Since 24 >= 18 is true and is_student is also true, both hold, so the whole thing is true.

If you change age to 15, then 15 >= 18 is false, and no matter whether is_student is true or not, the whole thing is false, so nothing is printed.

|| — OR

As long as either condition holds, the result is true:

fn main() {
    let is_weekend = false;
    let is_holiday = true;

    if is_weekend || is_holiday {
        println!("No work today!");
    }
}

Although is_weekend is false, is_holiday is true — one true is all it takes.

! — NOT

Turns true into false and false into true:

fn main() {
    let raining = false;

    if !raining {
        println!("Let's go out for a walk!");
    }
}

raining is false; with ! in front it becomes true, so the condition holds.

You can read it as: “If it’s not raining, go out for a walk.”

Recap

• && (and): true only when both sides are true.
• || (or): true as long as either side is true.
• ! (not): turns true into false and false into true.
• Combine multiple conditions with logical operators to write more precise checks.