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Add entry-like methods to HashSet
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This is ported from rust-lang/rust#60894
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Amanieu committed Jul 4, 2019
1 parent 03da6ab commit 20ec1fb
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Showing 2 changed files with 54 additions and 2 deletions.
6 changes: 4 additions & 2 deletions src/map.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1257,11 +1257,13 @@ pub struct RawEntryBuilderMut<'a, K, V, S> {
///
/// This is a lower-level version of [`Entry`].
///
/// This `enum` is constructed from the [`raw_entry`] method on [`HashMap`].
/// This `enum` is constructed through the [`raw_entry_mut`] method on [`HashMap`],
/// then calling one of the methods of that [`RawEntryBuilderMut`].
///
/// [`HashMap`]: struct.HashMap.html
/// [`Entry`]: enum.Entry.html
/// [`raw_entry`]: struct.HashMap.html#method.raw_entry
/// [`raw_entry_mut`]: struct.HashMap.html#method.raw_entry_mut
/// [`RawEntryBuilderMut`]: struct.RawEntryBuilderMut.html
pub enum RawEntryMut<'a, K, V, S> {
/// An occupied entry.
Occupied(RawOccupiedEntryMut<'a, K, V>),
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50 changes: 50 additions & 0 deletions src/set.rs
Original file line number Diff line number Diff line change
Expand Up @@ -601,6 +601,56 @@ where
self.map.get_key_value(value).map(|(k, _)| k)
}

/// Inserts the given `value` into the set if it is not present, then
/// returns a reference to the value in the set.
///
/// # Examples
///
/// ```
/// use hashbrown::HashSet;
///
/// let mut set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
/// assert_eq!(set.len(), 3);
/// assert_eq!(set.get_or_insert(2), &2);
/// assert_eq!(set.get_or_insert(100), &100);
/// assert_eq!(set.len(), 4); // 100 was inserted
/// ```
#[inline]
pub fn get_or_insert(&mut self, value: T) -> &T {
// Although the raw entry gives us `&mut T`, we only return `&T` to be consistent with
// `get`. Key mutation is "raw" because you're not supposed to affect `Eq` or `Hash`.
self.map.raw_entry_mut().from_key(&value).or_insert(value, ()).0
}

/// Inserts a value computed from `f` into the set if the given `value` is
/// not present, then returns a reference to the value in the set.
///
/// # Examples
///
/// ```
/// use hashbrown::HashSet;
///
/// let mut set: HashSet<String> = ["cat", "dog", "horse"]
/// .iter().map(|&pet| pet.to_owned()).collect();
///
/// assert_eq!(set.len(), 3);
/// for &pet in &["cat", "dog", "fish"] {
/// let value = set.get_or_insert_with(pet, str::to_owned);
/// assert_eq!(value, pet);
/// }
/// assert_eq!(set.len(), 4); // a new "fish" was inserted
/// ```
#[inline]
pub fn get_or_insert_with<Q: ?Sized, F>(&mut self, value: &Q, f: F) -> &T
where T: Borrow<Q>,
Q: Hash + Eq,
F: FnOnce(&Q) -> T
{
// Although the raw entry gives us `&mut T`, we only return `&T` to be consistent with
// `get`. Key mutation is "raw" because you're not supposed to affect `Eq` or `Hash`.
self.map.raw_entry_mut().from_key(value).or_insert_with(|| (f(value), ())).0
}

/// Returns `true` if `self` has no elements in common with `other`.
/// This is equivalent to checking for an empty intersection.
///
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