Error Handling in Rust that Every Beginner should Know (Rust Way)

cicle_equation.rs

fn square(s: &str) -> Result<f64, ParseFloatError> {
    s.parse::<f64>().map (|i| i * i)
}

fn calculate(x: &str, y: &str) -> Result<f64, ParseFloatError> {
    let x2 = square(x)?;
    let y2 = square(y)?;
    Ok((x2 + y2).sqrt())
}

println!("{:?}", calculate("2", "2")); // Ok(2.8284271247461903)
println!("{:?}", calculate("2", "?")); // Err(ParseFloatError { kind: Invalid })