gistfile1.rs

for x in 0..10 {
    let promise = Promise::<u32,&str>::new(move || { 
        match x {
            0 => Err("Division by zero"),
            _ => Ok(x * 2)
        }
    }).success(move |res| {
        assert_eq!(res, x * 2);
        Ok(res * 2) 
    }).success(|res| {
        Ok(format!("{}", res))
    }).fail(|error| {
        assert_eq!(error, "Division by zero");
        Err(error)
    }) ;
  
    let result = promise.sync();
  
    match x {
        0 => assert!(result.is_err()),
        _ => {
            assert!(result.is_ok());
            assert_eq!(result.unwrap(), format!("{}", x * 4));
        }
    }
}