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Clarifying that .map() returns None if None.

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Ame 2023-02-03 04:54:27 -06:00
parent 9545094994
commit c2b65ffe29
1 changed files with 4 additions and 2 deletions
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6
library/core/src/option.rs
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@ -943,7 +943,7 @@ impl<T> Option<T> {
// Transforming contained values
/////////////////////////////////////////////////////////////////////////
/// Maps an `Option<T>` to `Option<U>` by applying a function to a contained value.
/// Maps an `Option<T>` to `Option<U>` by applying a function to a contained value (if `Some`) or return `None` (if `None`).
///
/// # Examples
///
@ -955,8 +955,10 @@ impl<T> Option<T> {
/// let maybe_some_string = Some(String::from("Hello, World!"));
/// // `Option::map` takes self *by value*, consuming `maybe_some_string`
/// let maybe_some_len = maybe_some_string.map(|s| s.len());
///
/// assert_eq!(maybe_some_len, Some(13));
///
/// let x: Option<&str> = None;
/// assert_eq!(x.map(|s| s.len()), None);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]