If Else in Rust

Branching with if and else in Rust is straightforward.

fn main() {
    // Here's a basic example.
    if 7 % 2 == 0 {
        println!("7 is even");
    } else {
        println!("7 is odd");
    }

    // You can have an `if` statement without an else.
    if 8 % 4 == 0 {
        println!("8 is divisible by 4");
    }

    // Logical operators like `&&` and `||` are often
    // useful in conditions.
    if 8 % 2 == 0 || 7 % 2 == 0 {
        println!("either 8 or 7 are even");
    }

    // A statement can precede conditionals; any variables
    // declared in this statement are available in the current
    // and all subsequent branches.
    let num = 9;
    if num < 0 {
        println!("{} is negative", num);
    } else if num < 10 {
        println!("{} has 1 digit", num);
    } else {
        println!("{} has multiple digits", num);
    }
}

To run the program:

$ rustc if_else.rs
$ ./if_else
7 is odd
8 is divisible by 4
either 8 or 7 are even
9 has 1 digit

Note that you don’t need parentheses around conditions in Rust, but the braces are required.

Rust, like many modern languages, does not have a ternary operator. Instead, you can use the if expression, which can return a value:

let x = if condition { value1 } else { value2 };

This is more flexible and consistent with the rest of the language than a dedicated ternary operator.

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If Else in Rust