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Option::and_then basic example: show failure

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cyqsimon 2022-02-12 12:23:38 +08:00
parent adfac00f45
commit 160faf1b30
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library/core/src/option.rs
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@ -1207,10 +1207,13 @@ impl<T> Option<T> {
/// # Examples
///
/// ```
/// fn squared_string(x: u32) -> Option<String> { Some((x * x).to_string()) }
/// fn sq_then_to_string(x: u32) -> Option<String> {
/// x.checked_mul(x).map(|sq| sq.to_string())
/// }
///
/// assert_eq!(Some(2).and_then(squared_string), Some(4.to_string()));
/// assert_eq!(None.and_then(squared_string), None);
/// assert_eq!(Some(2).and_then(sq_then_to_string), Some(4.to_string()));
/// assert_eq!(Some(1_000_000).and_then(sq_then_to_string), None); // overflowed!
/// assert_eq!(None.and_then(sq_then_to_string), None);
/// ```
///
/// Often used to chain fallible operations that may return [`None`].