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// Result-returning functions, Ok/Err construction, and matching on both.
#[derive(Debug, PartialEq)]
enum Error {
    TooBig,
}

fn halve(n: i32) -> Result<i32, Error> {
    if n > 100 {
        Err(Error::TooBig)
    } else {
        Ok(n / 2)
    }
}

fn main() {
    for n in [10, 200] {
        match halve(n) {
            Ok(v) => println!("ok {}", v),
            Err(e) => println!("err {:?}", e),
        }
    }
    println!("{:?}", halve(8));
    println!("{}", halve(8).unwrap());
    println!("{} {}", halve(8).is_ok(), halve(500).is_err());
}