Conditionals

Much of the Rust syntax will be familiar to you from C, C++ or Java:

• Blocks are delimited by curly braces.
• Line comments are started with //, block comments are delimited by /* ... */.
• Keywords like if and while work the same.
• Variable assignment is done with =, comparison is done with ==.

if expressions

You use if expressions exactly like if statements in other languages:

fn main() {
    let x = 10;
    if x < 20 {
        println!("small");
    } else if x < 100 {
        println!("biggish");
    } else {
        println!("huge");
    }
}

In addition, you can use if as an expression. The last expression of each block becomes the value of the if expression:

fn main() {
    let x = 10;
    let size = if x < 20 { "small" } else { "large" };
    println!("number size: {}", size);
}