Function double_first

0a_error_handling/rust/boilerplate.rs:17–21

(vec: Vec<&str>)

impl error::Error for EmptyVec {}

fn double_first(vec: Vec<&str>) -> Result<i32> {
    let first = vec.first().ok_or(EmptyVec)?;
    let parsed = first.parse::<i32>()?;
    Ok(2 * parsed)
}

fn print(result: Result<i32>) {
    match result {