| We've seen that the `Option` enum can be used as a return value from functions |
| that may fail, where `None` can be returned to indicate failure. However, |
| sometimes is important to express *why* an operation failed. To do this we have |
| the `Result` enum. |
| |
| The `Result<T, E>` enum has two variants: |
| |
| * `Ok(value)` which indicates that the operation succeeded, and wraps the |
| `value` returned by the operation. (`value` has type `T`) |
| * `Err(why)`, which indicates that the operation failed, and wraps `why`, |
| which (hopefully) explains the cause of the failure. (`why` has type `E`) |
| |
| {result.play} |
