Propagating Errors with the ? Operator

Propagating Errors with the ? Operator

The ? operator unwraps Ok values or immediately returns early with Err:

fn parse_and_double(s: &str) -> Result<i32, std::num::ParseIntError> {
    let n = s.trim().parse::<i32>()?;
    Ok(n * 2)
}

fn main() {
    match parse_and_double("42") {
        Ok(v) => println!("Result: {}", v),
        Err(e) => println!("Parse failed: {}", e),
    }
}