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Add examples using add_modify to btree

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Updated the btree's documentation to include two references to
add_modify.

The first is when the `Entry` API is mentioned at the beginning. With
the same reasoning as HashMap's documentation, I thought it would best
to keep `attack`, but show the `mana` example.

The second is with the `entry` function that is used for the `Entry`
API. The code example was a perfect use for `add_modify`, which is why
it was changed to reflect that.
This commit is contained in:
KarlWithK 2022-06-15 02:04:18 -05:00
parent d3d22e1e66
commit cec72acdca
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GPG Key ID: 183357B41320BB2B
1 changed files with 6 additions and 1 deletions
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7
library/alloc/src/collections/btree/map.rs
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@ -159,6 +159,9 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
/// // update a key, guarding against the key possibly not being set
/// let stat = player_stats.entry("attack").or_insert(100);
/// *stat += random_stat_buff();
///
/// // modify an entry before an insert with in-place mutation
/// player_stats.entry("mana").and_modify(|mana| *mana += 200).or_insert(100);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(not(test), rustc_diagnostic_item = "BTreeMap")]
@ -1135,10 +1138,12 @@ impl<K, V> BTreeMap<K, V> {
///
/// // count the number of occurrences of letters in the vec
/// for x in ["a", "b", "a", "c", "a", "b"] {
/// *count.entry(x).or_insert(0) += 1;
/// count.entry(x).and_modify(|curr| *curr += 1).or_insert(1);
/// }
///
/// assert_eq!(count["a"], 3);
/// assert_eq!(count["b"], 2);
/// assert_eq!(count["1"], 1);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn entry(&mut self, key: K) -> Entry<'_, K, V>