Comparison Operators

Goal of This Episode

Learn to use comparison operators to compare sizes and check equality.

Main Text

So far we’ve been doing math, but there’s another very important kind of operation in programming — comparison.

The result of a comparison isn’t a number; it’s true or false.

== Equal To

fn main() {
    println!("{}", 5 == 5);
}

Is 5 equal to 5? Yes, so it’s true.

Careful here: it’s two equals signs ==, not one. A single equals sign = is for assigning values to variables (let x = 5;); two equals signs == are for comparing.

!= Not Equal To

fn main() {
    println!("{}", 5 != 3);
}

Is 5 not equal to 3? Correct.

< Less Than

fn main() {
    println!("{}", 3 < 5);
}

3 is less than 5.

> Greater Than

fn main() {
    println!("{}", 10 > 7);
}

10 is greater than 7.

<= Less Than or Equal To

fn main() {
    println!("{}", 5 <= 5);
}

Is 5 less than or equal to 5? Being equal counts too.

>= Greater Than or Equal To

fn main() {
    println!("{}", 8 >= 10);
}

Is 8 greater than or equal to 10? No.

At a Glance

Recap

• The six comparison operators: ==, !=, <, >, <=, >=.
• The result of a comparison is true or false.
• == (two equals signs) compares; = (one equals sign) assigns. Don’t mix them up.