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Implement owned ops for HashSet and BTreeSet #109402

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Implement owned ops for HashSet and BTreeSet #109402

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b70c88e
Drive-by cleanup: simplify documentation of `HashSet` ops
WaffleLapkin Mar 20, 2023
c09d35d
Add implementations of `ops` for `HashSet` that keep ownership
WaffleLapkin Mar 20, 2023
cb5ee7c
Add implementations of `ops` for `BTreeSet` that keep ownership
WaffleLapkin Mar 20, 2023
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116 changes: 116 additions & 0 deletions library/alloc/src/collections/btree/set.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1404,6 +1404,37 @@ impl<T: Ord + Clone, A: Allocator + Clone> Sub<&BTreeSet<T, A>> for &BTreeSet<T,
}
}

#[stable(feature = "set_owned_ops", since = "CURRENT_RUSTC_VERSION")]
impl<T: Ord, A: Allocator + Clone> Sub<&BTreeSet<T, A>> for BTreeSet<T, A> {
type Output = BTreeSet<T, A>;

/// Returns the difference of `self` and `rhs` as a new `BTreeSet<T>`.
///
/// # Examples
///
/// ```
/// use std::collections::BTreeSet;
///
/// let a = BTreeSet::from([1, 2, 3]);
/// let b = BTreeSet::from([3, 4, 5]);
///
/// let result = a - &b;
/// assert_eq!(result, BTreeSet::from([1, 2]));
/// ```
fn sub(mut self, rhs: &BTreeSet<T, A>) -> BTreeSet<T, A> {
// Iterate the smaller set, removing elements that are in `rhs` from `self`
if self.len() <= rhs.len() {
self.retain(|e| !rhs.contains(e));
} else {
rhs.iter().for_each(|e| {
self.remove(e);
})
}

self
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Ord + Clone, A: Allocator + Clone> BitXor<&BTreeSet<T, A>> for &BTreeSet<T, A> {
type Output = BTreeSet<T, A>;
Expand All @@ -1429,6 +1460,37 @@ impl<T: Ord + Clone, A: Allocator + Clone> BitXor<&BTreeSet<T, A>> for &BTreeSet
}
}

#[stable(feature = "set_owned_ops", since = "CURRENT_RUSTC_VERSION")]
impl<T: Ord, A: Allocator + Clone> BitXor<BTreeSet<T, A>> for BTreeSet<T, A> {
type Output = BTreeSet<T, A>;

/// Returns the symmetric difference of `self` and `rhs` as a new `BTreeSet<T>`.
///
/// # Examples
///
/// ```
/// use std::collections::BTreeSet;
///
/// let a = BTreeSet::from([1, 2, 3]);
/// let b = BTreeSet::from([2, 3, 4]);
///
/// let result = a ^ b;
/// assert_eq!(result, BTreeSet::from([1, 4]));
/// ```
fn bitxor(self, rhs: BTreeSet<T, A>) -> BTreeSet<T, A> {
// Iterate through the smaller set
let [mut a, mut b] = minmax_by_key(self, rhs, BTreeSet::len);

// This is essentially
// a = a - b (retain elements that are *not* in b)
// b = b - a (remove all elements that are in a)
a.retain(|e| !b.remove(e));

// Union of the differences
a | b
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Ord + Clone, A: Allocator + Clone> BitAnd<&BTreeSet<T, A>> for &BTreeSet<T, A> {
type Output = BTreeSet<T, A>;
Expand All @@ -1454,6 +1516,29 @@ impl<T: Ord + Clone, A: Allocator + Clone> BitAnd<&BTreeSet<T, A>> for &BTreeSet
}
}

#[stable(feature = "set_owned_ops", since = "CURRENT_RUSTC_VERSION")]
impl<T: Ord, A: Allocator + Clone> BitAnd<&BTreeSet<T, A>> for BTreeSet<T, A> {
type Output = BTreeSet<T, A>;

/// Returns the intersection of `self` and `rhs` as a new `BTreeSet<T>`.
///
/// # Examples
///
/// ```
/// use std::collections::BTreeSet;
///
/// let a = BTreeSet::from([1, 2, 3]);
/// let b = BTreeSet::from([2, 3, 4]);
///
/// let result = a & &b;
/// assert_eq!(result, BTreeSet::from([2, 3]));
/// ```
fn bitand(mut self, rhs: &BTreeSet<T, A>) -> BTreeSet<T, A> {
self.retain(|e| rhs.contains(e));
self
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Ord + Clone, A: Allocator + Clone> BitOr<&BTreeSet<T, A>> for &BTreeSet<T, A> {
type Output = BTreeSet<T, A>;
Expand All @@ -1479,6 +1564,33 @@ impl<T: Ord + Clone, A: Allocator + Clone> BitOr<&BTreeSet<T, A>> for &BTreeSet<
}
}

#[stable(feature = "set_owned_ops", since = "CURRENT_RUSTC_VERSION")]
impl<T: Ord, A: Allocator + Clone> BitOr<BTreeSet<T, A>> for BTreeSet<T, A> {
type Output = BTreeSet<T, A>;

/// Returns the union of `self` and `rhs` as a new `BTreeSet<T>`.
///
/// # Examples
///
/// ```
/// use std::collections::BTreeSet;
///
/// let a = BTreeSet::from([1, 2, 3]);
/// let b = BTreeSet::from([3, 4, 5]);
///
/// let result = a | b;
/// assert_eq!(result, BTreeSet::from([1, 2, 3, 4, 5]));
/// ```
fn bitor(self, rhs: BTreeSet<T, A>) -> BTreeSet<T, A> {
// Try to avoid unnecessary moves, by keeping set with the bigger length
let [a, mut b] = minmax_by_key(self, rhs, BTreeSet::len);

b.extend(a);

b
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Debug, A: Allocator + Clone> Debug for BTreeSet<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
Expand Down Expand Up @@ -1789,5 +1901,9 @@ impl<'a, T: Ord> Iterator for Union<'a, T> {
#[stable(feature = "fused", since = "1.26.0")]
impl<T: Ord> FusedIterator for Union<'_, T> {}

fn minmax_by_key<T, K: Ord>(a: T, b: T, k: impl Fn(&T) -> K) -> [T; 2] {
if k(&a) <= k(&b) { [a, b] } else { [b, a] }
}

#[cfg(test)]
mod tests;
177 changes: 141 additions & 36 deletions library/std/src/collections/hash/set.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1138,21 +1138,46 @@ where
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([3, 4, 5]);
///
/// let set = &a | &b;
///
/// let mut i = 0;
/// let expected = [1, 2, 3, 4, 5];
/// for x in &set {
/// assert!(expected.contains(x));
/// i += 1;
/// }
/// assert_eq!(i, expected.len());
/// let result = &a | &b;
/// assert_eq!(result, HashSet::from([1, 2, 3, 4, 5]));
/// ```
fn bitor(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
self.union(rhs).cloned().collect()
}
}

#[stable(feature = "set_owned_ops", since = "CURRENT_RUSTC_VERSION")]
impl<T, S> BitOr<HashSet<T, S>> for HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
type Output = HashSet<T, S>;

/// Returns the union of `self` and `rhs` as a new `HashSet<T, S>`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([3, 4, 5]);
///
/// let result = a | b;
/// assert_eq!(result, HashSet::from([1, 2, 3, 4, 5]));
/// ```
fn bitor(self, rhs: HashSet<T, S>) -> HashSet<T, S> {
// Try to avoid allocations by keeping set with the bigger capacity,
// try to avoid unnecessary moves, by keeping set with the bigger length
let [a, mut b] = minmax_by_key(self, rhs, |set| (set.capacity(), set.len()));

b.extend(a);

b
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> BitAnd<&HashSet<T, S>> for &HashSet<T, S>
where
Expand All @@ -1171,21 +1196,41 @@ where
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([2, 3, 4]);
///
/// let set = &a & &b;
///
/// let mut i = 0;
/// let expected = [2, 3];
/// for x in &set {
/// assert!(expected.contains(x));
/// i += 1;
/// }
/// assert_eq!(i, expected.len());
/// let result = &a & &b;
/// assert_eq!(result, HashSet::from([2, 3]));
/// ```
fn bitand(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
self.intersection(rhs).cloned().collect()
}
}

#[stable(feature = "set_owned_ops", since = "CURRENT_RUSTC_VERSION")]
impl<T, S> BitAnd<&HashSet<T, S>> for HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
type Output = HashSet<T, S>;

/// Returns the intersection of `self` and `rhs` as a new `HashSet<T, S>`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([2, 3, 4]);
///
/// let result = a & &b;
/// assert_eq!(result, HashSet::from([2, 3]));
/// ```
fn bitand(mut self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
self.retain(|e| rhs.contains(e));
self
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> BitXor<&HashSet<T, S>> for &HashSet<T, S>
where
Expand All @@ -1204,21 +1249,49 @@ where
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([3, 4, 5]);
///
/// let set = &a ^ &b;
///
/// let mut i = 0;
/// let expected = [1, 2, 4, 5];
/// for x in &set {
/// assert!(expected.contains(x));
/// i += 1;
/// }
/// assert_eq!(i, expected.len());
/// let result = &a ^ &b;
/// assert_eq!(result, HashSet::from([1, 2, 4, 5]));
/// ```
fn bitxor(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
self.symmetric_difference(rhs).cloned().collect()
}
}

#[stable(feature = "set_owned_ops", since = "CURRENT_RUSTC_VERSION")]
impl<T, S> BitXor<HashSet<T, S>> for HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
type Output = HashSet<T, S>;

/// Returns the symmetric difference of `self` and `rhs` as a new `HashSet<T, S>`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([3, 4, 5]);
///
/// let result = a ^ b;
/// assert_eq!(result, HashSet::from([1, 2, 4, 5]));
/// ```
fn bitxor(self, rhs: HashSet<T, S>) -> HashSet<T, S> {
// Iterate through the smaller set
let [mut a, mut b] = minmax_by_key(self, rhs, HashSet::len);

// This is essentially
// a = a - b (retain elements that are *not* in b)
// b = b - a (remove all elements that are in a)
a.retain(|e| !b.remove(e));

// Union of the differences
a | b
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Sub<&HashSet<T, S>> for &HashSet<T, S>
where
Expand All @@ -1237,21 +1310,49 @@ where
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([3, 4, 5]);
///
/// let set = &a - &b;
///
/// let mut i = 0;
/// let expected = [1, 2];
/// for x in &set {
/// assert!(expected.contains(x));
/// i += 1;
/// }
/// assert_eq!(i, expected.len());
/// let result = &a - &b;
/// assert_eq!(result, HashSet::from([1, 2]));
/// ```
fn sub(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
self.difference(rhs).cloned().collect()
}
}

#[stable(feature = "set_owned_ops", since = "CURRENT_RUSTC_VERSION")]
impl<T, S> Sub<&HashSet<T, S>> for HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
type Output = HashSet<T, S>;

/// Returns the difference of `self` and `rhs` as a new `HashSet<T, S>`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([3, 4, 5]);
///
/// let result = a - &b;
/// assert_eq!(result, HashSet::from([1, 2]));
/// ```
fn sub(mut self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
// Iterate the smaller set, removing elements that are in `rhs` from `self`
if self.len() <= rhs.len() {
self.retain(|e| !rhs.contains(e));
} else {
rhs.iter().for_each(|e| {
self.remove(e);
})
}

self
}
}

/// An iterator over the items of a `HashSet`.
///
/// This `struct` is created by the [`iter`] method on [`HashSet`].
Expand Down Expand Up @@ -1843,3 +1944,7 @@ fn assert_covariance() {
d
}
}

fn minmax_by_key<T, K: Ord>(a: T, b: T, k: impl Fn(&T) -> K) -> [T; 2] {
if k(&a) <= k(&b) { [a, b] } else { [b, a] }
}