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## BTreeSet

# Struct BTreeSet

1.36.0 · Source

    pub struct BTreeSet<T, A: Allocator + Clone = Global> { /* private fields */ }

Expand description

An ordered set based on a B-Tree.

See `BTreeMap`’s documentation for a detailed discussion of this collection’s performance benefits and drawbacks.

It is a logic error for an item to be modified in such a way that the item’s ordering relative to any other item, as determined by the `Ord` trait, changes while it is in the set. This is normally only possible through `Cell`, `RefCell`, global state, I/O, or unsafe code. The behavior resulting from such a logic error is not specified, but will be encapsulated to the `BTreeSet` that observed the logic error and not result in undefined behavior. This could include panics, incorrect results, aborts, memory leaks, and non-termination.

Iterators returned by `BTreeSet::iter` and `BTreeSet::into_iter` produce their items in order, and take worst-case logarithmic and amortized constant time per item returned.

## §Examples

    use std::collections::BTreeSet;

    // Type inference lets us omit an explicit type signature (which
    // would be `BTreeSet<&str>` in this example).
    let mut books = BTreeSet::new();

    // Add some books.
    books.insert("A Dance With Dragons");
    books.insert("To Kill a Mockingbird");
    books.insert("The Odyssey");
    books.insert("The Great Gatsby");

    // Check for a specific one.
    if !books.contains("The Winds of Winter") {
        println!("We have {} books, but The Winds of Winter ain't one.",
                 books.len());
    }

    // Remove a book.
    books.remove("The Odyssey");

    // Iterate over everything.
    for book in &books {
        println!("{book}");
    }

A `BTreeSet` with a known list of items can be initialized from an array:

    use std::collections::BTreeSet;

    let set = BTreeSet::from([1, 2, 3]);

## Implementations§

Source§

### impl<T> BTreeSet<T>

1.0.0 (const: 1.66.0) · Source

#### pub const fn new() -> BTreeSet<T>

Makes a new, empty `BTreeSet`.

Does not allocate anything on its own.

##### §Examples

    use std::collections::BTreeSet;

    let mut set: BTreeSet<i32> = BTreeSet::new();

Source§

### impl<T, A: Allocator + Clone> BTreeSet<T, A>

Source

#### pub const fn new_in(alloc: A) -> BTreeSet<T, A>

🔬This is a nightly-only experimental API. (`btreemap_alloc` #32838)

Makes a new `BTreeSet` with a reasonable choice of B.

##### §Examples

    use std::collections::BTreeSet;
    use std::alloc::Global;

    let set: BTreeSet<i32> = BTreeSet::new_in(Global);

1.17.0 · Source

#### pub fn range<K, R>(&self, range: R) -> Range<'_, T> ⓘ
where K: Ord + ?Sized, T: Borrow<K> + Ord, R: RangeBounds<K>,

Constructs a double-ended iterator over a sub-range of elements in the set. The simplest way is to use the range syntax `min..max`, thus `range(min..max)` will yield elements from min (inclusive) to max (exclusive). The range may also be entered as `(Bound<T>, Bound<T>)`, so for example `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive range from 4 to 10.

##### §Panics

Panics if range `start > end`. Panics if range `start == end` and both bounds are `Excluded`.

##### §Examples

    use std::collections::BTreeSet;
    use std::ops::Bound::Included;

    let mut set = BTreeSet::new();
    set.insert(3);
    set.insert(5);
    set.insert(8);
    for &elem in set.range((Included(&4), Included(&8))) {
        println!("{elem}");
    }
    assert_eq!(Some(&5), set.range(4..).next());

1.0.0 · Source

#### pub fn difference<'a>( &'a self, other: &'a BTreeSet<T, A>, ) -> Difference<'a, T, A> ⓘ
where T: Ord,

Visits the elements representing the difference, i.e., the elements that are in `self` but not in `other`, in ascending order.

##### §Examples

    use std::collections::BTreeSet;

    let mut a = BTreeSet::new();
    a.insert(1);
    a.insert(2);

    let mut b = BTreeSet::new();
    b.insert(2);
    b.insert(3);

    let diff: Vec<_> = a.difference(&b).cloned().collect();
    assert_eq!(diff, [1]);

1.0.0 · Source

#### pub fn symmetric_difference<'a>( &'a self, other: &'a BTreeSet<T, A>, ) -> SymmetricDifference<'a, T> ⓘ
where T: Ord,

Visits the elements representing the symmetric difference, i.e., the elements that are in `self` or in `other` but not in both, in ascending order.

##### §Examples

    use std::collections::BTreeSet;

    let mut a = BTreeSet::new();
    a.insert(1);
    a.insert(2);

    let mut b = BTreeSet::new();
    b.insert(2);
    b.insert(3);

    let sym_diff: Vec<_> = a.symmetric_difference(&b).cloned().collect();
    assert_eq!(sym_diff, [1, 3]);

1.0.0 · Source

#### pub fn intersection<'a>( &'a self, other: &'a BTreeSet<T, A>, ) -> Intersection<'a, T, A> ⓘ
where T: Ord,

Visits the elements representing the intersection, i.e., the elements that are both in `self` and `other`, in ascending order.

##### §Examples

    use std::collections::BTreeSet;

    let mut a = BTreeSet::new();
    a.insert(1);
    a.insert(2);

    let mut b = BTreeSet::new();
    b.insert(2);
    b.insert(3);

    let intersection: Vec<_> = a.intersection(&b).cloned().collect();
    assert_eq!(intersection, [2]);

1.0.0 · Source

#### pub fn union<'a>(&'a self, other: &'a BTreeSet<T, A>) -> Union<'a, T> ⓘ
where T: Ord,

Visits the elements representing the union, i.e., all the elements in `self` or `other`, without duplicates, in ascending order.

##### §Examples

    use std::collections::BTreeSet;

    let mut a = BTreeSet::new();
    a.insert(1);

    let mut b = BTreeSet::new();
    b.insert(2);

    let union: Vec<_> = a.union(&b).cloned().collect();
    assert_eq!(union, [1, 2]);

1.0.0 · Source

#### pub fn clear(&mut self)
where A: Clone,

Clears the set, removing all elements.

##### §Examples

    use std::collections::BTreeSet;

    let mut v = BTreeSet::new();
    v.insert(1);
    v.clear();
    assert!(v.is_empty());

1.0.0 · Source

#### pub fn contains<Q>(&self, value: &Q) -> bool
where T: Borrow<Q> + Ord, Q: Ord + ?Sized,

Returns `true` if the set contains an element equal to the value.

The value may be any borrowed form of the set’s element type, but the ordering on the borrowed form must match the ordering on the element type.

##### §Examples

    use std::collections::BTreeSet;

    let set = BTreeSet::from([1, 2, 3]);
    assert_eq!(set.contains(&1), true);
    assert_eq!(set.contains(&4), false);

1.9.0 · Source

#### pub fn get<Q>(&self, value: &Q) -> Option<&T>
where T: Borrow<Q> + Ord, Q: Ord + ?Sized,

Returns a reference to the element in the set, if any, that is equal to the value.

The value may be any borrowed form of the set’s element type, but the ordering on the borrowed form must match the ordering on the element type.

##### §Examples

    use std::collections::BTreeSet;

    let set = BTreeSet::from([1, 2, 3]);
    assert_eq!(set.get(&2), Some(&2));
    assert_eq!(set.get(&4), None);

1.0.0 · Source

#### pub fn is_disjoint(&self, other: &BTreeSet<T, A>) -> bool
where T: Ord,

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

##### §Examples

    use std::collections::BTreeSet;

    let a = BTreeSet::from([1, 2, 3]);
    let mut b = BTreeSet::new();

    assert_eq!(a.is_disjoint(&b), true);
    b.insert(4);
    assert_eq!(a.is_disjoint(&b), true);
    b.insert(1);
    assert_eq!(a.is_disjoint(&b), false);

1.0.0 · Source

#### pub fn is_subset(&self, other: &BTreeSet<T, A>) -> bool
where T: Ord,

Returns `true` if the set is a subset of another, i.e., `other` contains at least all the elements in `self`.

##### §Examples

    use std::collections::BTreeSet;

    let sup = BTreeSet::from([1, 2, 3]);
    let mut set = BTreeSet::new();

    assert_eq!(set.is_subset(&sup), true);
    set.insert(2);
    assert_eq!(set.is_subset(&sup), true);
    set.insert(4);
    assert_eq!(set.is_subset(&sup), false);

1.0.0 · Source

#### pub fn is_superset(&self, other: &BTreeSet<T, A>) -> bool
where T: Ord,

Returns `true` if the set is a superset of another, i.e., `self` contains at least all the elements in `other`.

##### §Examples

    use std::collections::BTreeSet;

    let sub = BTreeSet::from([1, 2]);
    let mut set = BTreeSet::new();

    assert_eq!(set.is_superset(&sub), false);

    set.insert(0);
    set.insert(1);
    assert_eq!(set.is_superset(&sub), false);

    set.insert(2);
    assert_eq!(set.is_superset(&sub), true);

1.66.0 · Source

#### pub fn first(&self) -> Option<&T>
where T: Ord,

Returns a reference to the first element in the set, if any. This element is always the minimum of all elements in the set.

##### §Examples

Basic usage:

    use std::collections::BTreeSet;

    let mut set = BTreeSet::new();
    assert_eq!(set.first(), None);
    set.insert(1);
    assert_eq!(set.first(), Some(&1));
    set.insert(2);
    assert_eq!(set.first(), Some(&1));

1.66.0 · Source

#### pub fn last(&self) -> Option<&T>
where T: Ord,

Returns a reference to the last element in the set, if any. This element is always the maximum of all elements in the set.

##### §Examples

Basic usage:

    use std::collections::BTreeSet;

    let mut set = BTreeSet::new();
    assert_eq!(set.last(), None);
    set.insert(1);
    assert_eq!(set.last(), Some(&1));
    set.insert(2);
    assert_eq!(set.last(), Some(&2));

1.66.0 · Source

#### pub fn pop_first(&mut self) -> Option<T>
where T: Ord,

Removes the first element from the set and returns it, if any. The first element is always the minimum element in the set.

##### §Examples

    use std::collections::BTreeSet;

    let mut set = BTreeSet::new();

    set.insert(1);
    while let Some(n) = set.pop_first() {
        assert_eq!(n, 1);
    }
    assert!(set.is_empty());

1.66.0 · Source

#### pub fn pop_last(&mut self) -> Option<T>
where T: Ord,

Removes the last element from the set and returns it, if any. The last element is always the maximum element in the set.

##### §Examples

    use std::collections::BTreeSet;

    let mut set = BTreeSet::new();

    set.insert(1);
    while let Some(n) = set.pop_last() {
        assert_eq!(n, 1);
    }
    assert!(set.is_empty());

1.0.0 · Source

#### pub fn insert(&mut self, value: T) -> bool
where T: Ord,

Adds a value to the set.

Returns whether the value was newly inserted. That is:

- If the set did not previously contain an equal value, `true` is returned.
- If the set already contained an equal value, `false` is returned, and the entry is not updated.

See the module-level documentation for more.

##### §Examples

    use std::collections::BTreeSet;

    let mut set = BTreeSet::new();

    assert_eq!(set.insert(2), true);
    assert_eq!(set.insert(2), false);
    assert_eq!(set.len(), 1);

1.9.0 · Source

#### pub fn replace(&mut self, value: T) -> Option<T>
where T: Ord,

Adds a value to the set, replacing the existing element, if any, that is equal to the value. Returns the replaced element.

##### §Examples

    use std::collections::BTreeSet;

    let mut set = BTreeSet::new();
    set.insert(Vec::<i32>::new());

    assert_eq!(set.get(&[][..]).unwrap().capacity(), 0);
    set.replace(Vec::with_capacity(10));
    assert_eq!(set.get(&[][..]).unwrap().capacity(), 10);

Source

#### pub fn get_or_insert(&mut self, value: T) -> &T
where T: Ord,

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

Inserts the given `value` into the set if it is not present, then returns a reference to the value in the set.

##### §Examples

    #![feature(btree_set_entry)]

    use std::collections::BTreeSet;

    let mut set = BTreeSet::from([1, 2, 3]);
    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

Source

#### pub fn get_or_insert_with<Q, F>(&mut self, value: &Q, f: F) -> &T
where T: Borrow<Q> + Ord, Q: Ord + ?Sized, F: FnOnce(&Q) -> T,

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

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

    #![feature(btree_set_entry)]

    use std::collections::BTreeSet;

    let mut set: BTreeSet<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

Source

#### pub fn entry(&mut self, value: T) -> Entry<'_, T, A>
where T: Ord,

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

Gets the given value’s corresponding entry in the set for in-place manipulation.

##### §Examples

    #![feature(btree_set_entry)]

    use std::collections::BTreeSet;
    use std::collections::btree_set::Entry::*;

    let mut singles = BTreeSet::new();
    let mut dupes = BTreeSet::new();

    for ch in "a short treatise on fungi".chars() {
        if let Vacant(dupe_entry) = dupes.entry(ch) {
            // We haven't already seen a duplicate, so
            // check if we've at least seen it once.
            match singles.entry(ch) {
                Vacant(single_entry) => {
                    // We found a new character for the first time.
                    single_entry.insert()
                }
                Occupied(single_entry) => {
                    // We've already seen this once, "move" it to dupes.
                    single_entry.remove();
                    dupe_entry.insert();
                }
            }
        }
    }

    assert!(!singles.contains(&'t') && dupes.contains(&'t'));
    assert!(singles.contains(&'u') && !dupes.contains(&'u'));
    assert!(!singles.contains(&'v') && !dupes.contains(&'v'));

1.0.0 · Source

#### pub fn remove<Q>(&mut self, value: &Q) -> bool
where T: Borrow<Q> + Ord, Q: Ord + ?Sized,

If the set contains an element equal to the value, removes it from the set and drops it. Returns whether such an element was present.

The value may be any borrowed form of the set’s element type, but the ordering on the borrowed form must match the ordering on the element type.

##### §Examples

    use std::collections::BTreeSet;

    let mut set = BTreeSet::new();

    set.insert(2);
    assert_eq!(set.remove(&2), true);
    assert_eq!(set.remove(&2), false);

1.9.0 · Source

#### pub fn take<Q>(&mut self, value: &Q) -> Option<T>
where T: Borrow<Q> + Ord, Q: Ord + ?Sized,

Removes and returns the element in the set, if any, that is equal to the value.

The value may be any borrowed form of the set’s element type, but the ordering on the borrowed form must match the ordering on the element type.

##### §Examples

    use std::collections::BTreeSet;

    let mut set = BTreeSet::from([1, 2, 3]);
    assert_eq!(set.take(&2), Some(2));
    assert_eq!(set.take(&2), None);

1.53.0 · Source

#### pub fn retain<F>(&mut self, f: F)
where T: Ord, F: FnMut(&T) -> bool,

Retains only the elements specified by the predicate.

In other words, remove all elements `e` for which `f(&e)` returns `false`. The elements are visited in ascending order.

##### §Examples

    use std::collections::BTreeSet;

    let mut set = BTreeSet::from([1, 2, 3, 4, 5, 6]);
    // Keep only the even numbers.
    set.retain(|&k| k % 2 == 0);
    assert!(set.iter().eq([2, 4, 6].iter()));

1.11.0 · Source

#### pub fn append(&mut self, other: &mut Self)
where T: Ord, A: Clone,

Moves all elements from `other` into `self`, leaving `other` empty.

##### §Examples

    use std::collections::BTreeSet;

    let mut a = BTreeSet::new();
    a.insert(1);
    a.insert(2);
    a.insert(3);

    let mut b = BTreeSet::new();
    b.insert(3);
    b.insert(4);
    b.insert(5);

    a.append(&mut b);

    assert_eq!(a.len(), 5);
    assert_eq!(b.len(), 0);

    assert!(a.contains(&1));
    assert!(a.contains(&2));
    assert!(a.contains(&3));
    assert!(a.contains(&4));
    assert!(a.contains(&5));

1.11.0 · Source

#### pub fn split_off<Q: ?Sized + Ord>(&mut self, value: &Q) -> Self
where T: Borrow<Q> + Ord, A: Clone,

Splits the collection into two at the value. Returns a new collection with all elements greater than or equal to the value.

##### §Examples

Basic usage:

    use std::collections::BTreeSet;

    let mut a = BTreeSet::new();
    a.insert(1);
    a.insert(2);
    a.insert(3);
    a.insert(17);
    a.insert(41);

    let b = a.split_off(&3);

    assert_eq!(a.len(), 2);
    assert_eq!(b.len(), 3);

    assert!(a.contains(&1));
    assert!(a.contains(&2));

    assert!(b.contains(&3));
    assert!(b.contains(&17));
    assert!(b.contains(&41));

1.91.0 · Source

#### pub fn extract_if<F, R>( &mut self, range: R, pred: F, ) -> ExtractIf<'_, T, R, F, A> ⓘ
where T: Ord, R: RangeBounds<T>, F: FnMut(&T) -> bool,

Creates an iterator that visits elements in the specified range in ascending order and uses a closure to determine if an element should be removed.

If the closure returns `true`, the element is removed from the set and yielded. If the closure returns `false`, or panics, the element remains in the set and will not be yielded.

If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating or the iteration short-circuits, then the remaining elements will be retained. Use `extract_if().for_each(drop)` if you do not need the returned iterator, or `retain` with a negated predicate if you also do not need to restrict the range.

##### §Examples

    use std::collections::BTreeSet;

    // Splitting a set into even and odd values, reusing the original set:
    let mut set: BTreeSet<i32> = (0..8).collect();
    let evens: BTreeSet<_> = set.extract_if(.., |v| v % 2 == 0).collect();
    let odds = set;
    assert_eq!(evens.into_iter().collect::<Vec<_>>(), vec![0, 2, 4, 6]);
    assert_eq!(odds.into_iter().collect::<Vec<_>>(), vec![1, 3, 5, 7]);

    // Splitting a set into low and high halves, reusing the original set:
    let mut set: BTreeSet<i32> = (0..8).collect();
    let low: BTreeSet<_> = set.extract_if(0..4, |_v| true).collect();
    let high = set;
    assert_eq!(low.into_iter().collect::<Vec<_>>(), [0, 1, 2, 3]);
    assert_eq!(high.into_iter().collect::<Vec<_>>(), [4, 5, 6, 7]);

1.0.0 · Source

#### pub fn iter(&self) -> Iter<'_, T> ⓘ

Gets an iterator that visits the elements in the `BTreeSet` in ascending order.

##### §Examples

    use std::collections::BTreeSet;

    let set = BTreeSet::from([3, 1, 2]);
    let mut set_iter = set.iter();
    assert_eq!(set_iter.next(), Some(&1));
    assert_eq!(set_iter.next(), Some(&2));
    assert_eq!(set_iter.next(), Some(&3));
    assert_eq!(set_iter.next(), None);

1.0.0 (const: unstable) · Source

#### pub fn len(&self) -> usize

Returns the number of elements in the set.

##### §Examples

    use std::collections::BTreeSet;

    let mut v = BTreeSet::new();
    assert_eq!(v.len(), 0);
    v.insert(1);
    assert_eq!(v.len(), 1);

1.0.0 (const: unstable) · Source

#### pub fn is_empty(&self) -> bool

Returns `true` if the set contains no elements.

##### §Examples

    use std::collections::BTreeSet;

    let mut v = BTreeSet::new();
    assert!(v.is_empty());
    v.insert(1);
    assert!(!v.is_empty());

Source

#### pub fn lower_bound<Q>(&self, bound: Bound<&Q>) -> Cursor<'_, T>
where T: Borrow<Q> + Ord, Q: Ord + ?Sized,

🔬This is a nightly-only experimental API. (`btree_cursors` #107540)

Returns a `Cursor` pointing at the gap before the smallest element greater than the given bound.

Passing `Bound::Included(x)` will return a cursor pointing to the gap before the smallest element greater than or equal to `x`.

Passing `Bound::Excluded(x)` will return a cursor pointing to the gap before the smallest element greater than `x`.

Passing `Bound::Unbounded` will return a cursor pointing to the gap before the smallest element in the set.

##### §Examples

    #![feature(btree_cursors)]

    use std::collections::BTreeSet;
    use std::ops::Bound;

    let set = BTreeSet::from([1, 2, 3, 4]);

    let cursor = set.lower_bound(Bound::Included(&2));
    assert_eq!(cursor.peek_prev(), Some(&1));
    assert_eq!(cursor.peek_next(), Some(&2));

    let cursor = set.lower_bound(Bound::Excluded(&2));
    assert_eq!(cursor.peek_prev(), Some(&2));
    assert_eq!(cursor.peek_next(), Some(&3));

    let cursor = set.lower_bound(Bound::Unbounded);
    assert_eq!(cursor.peek_prev(), None);
    assert_eq!(cursor.peek_next(), Some(&1));

Source

#### pub fn lower_bound_mut<Q>(&mut self, bound: Bound<&Q>) -> CursorMut<'_, T, A>
where T: Borrow<Q> + Ord, Q: Ord + ?Sized,

🔬This is a nightly-only experimental API. (`btree_cursors` #107540)

Returns a `CursorMut` pointing at the gap before the smallest element greater than the given bound.

Passing `Bound::Included(x)` will return a cursor pointing to the gap before the smallest element greater than or equal to `x`.

Passing `Bound::Excluded(x)` will return a cursor pointing to the gap before the smallest element greater than `x`.

Passing `Bound::Unbounded` will return a cursor pointing to the gap before the smallest element in the set.

##### §Examples

    #![feature(btree_cursors)]

    use std::collections::BTreeSet;
    use std::ops::Bound;

    let mut set = BTreeSet::from([1, 2, 3, 4]);

    let mut cursor = set.lower_bound_mut(Bound::Included(&2));
    assert_eq!(cursor.peek_prev(), Some(&1));
    assert_eq!(cursor.peek_next(), Some(&2));

    let mut cursor = set.lower_bound_mut(Bound::Excluded(&2));
    assert_eq!(cursor.peek_prev(), Some(&2));
    assert_eq!(cursor.peek_next(), Some(&3));

    let mut cursor = set.lower_bound_mut(Bound::Unbounded);
    assert_eq!(cursor.peek_prev(), None);
    assert_eq!(cursor.peek_next(), Some(&1));

Source

#### pub fn upper_bound<Q>(&self, bound: Bound<&Q>) -> Cursor<'_, T>
where T: Borrow<Q> + Ord, Q: Ord + ?Sized,

🔬This is a nightly-only experimental API. (`btree_cursors` #107540)

Returns a `Cursor` pointing at the gap after the greatest element smaller than the given bound.

Passing `Bound::Included(x)` will return a cursor pointing to the gap after the greatest element smaller than or equal to `x`.

Passing `Bound::Excluded(x)` will return a cursor pointing to the gap after the greatest element smaller than `x`.

Passing `Bound::Unbounded` will return a cursor pointing to the gap after the greatest element in the set.

##### §Examples

    #![feature(btree_cursors)]

    use std::collections::BTreeSet;
    use std::ops::Bound;

    let set = BTreeSet::from([1, 2, 3, 4]);

    let cursor = set.upper_bound(Bound::Included(&3));
    assert_eq!(cursor.peek_prev(), Some(&3));
    assert_eq!(cursor.peek_next(), Some(&4));

    let cursor = set.upper_bound(Bound::Excluded(&3));
    assert_eq!(cursor.peek_prev(), Some(&2));
    assert_eq!(cursor.peek_next(), Some(&3));

    let cursor = set.upper_bound(Bound::Unbounded);
    assert_eq!(cursor.peek_prev(), Some(&4));
    assert_eq!(cursor.peek_next(), None);

Source

#### pub fn upper_bound_mut<Q>(&mut self, bound: Bound<&Q>) -> CursorMut<'_, T, A>
where T: Borrow<Q> + Ord, Q: Ord + ?Sized,

🔬This is a nightly-only experimental API. (`btree_cursors` #107540)

Returns a `CursorMut` pointing at the gap after the greatest element smaller than the given bound.

Passing `Bound::Included(x)` will return a cursor pointing to the gap after the greatest element smaller than or equal to `x`.

Passing `Bound::Excluded(x)` will return a cursor pointing to the gap after the greatest element smaller than `x`.

Passing `Bound::Unbounded` will return a cursor pointing to the gap after the greatest element in the set.

##### §Examples

    #![feature(btree_cursors)]

    use std::collections::BTreeSet;
    use std::ops::Bound;

    let mut set = BTreeSet::from([1, 2, 3, 4]);

    let mut cursor = set.upper_bound_mut(Bound::Included(&3));
    assert_eq!(cursor.peek_prev(), Some(&3));
    assert_eq!(cursor.peek_next(), Some(&4));

    let mut cursor = set.upper_bound_mut(Bound::Excluded(&3));
    assert_eq!(cursor.peek_prev(), Some(&2));
    assert_eq!(cursor.peek_next(), Some(&3));

    let mut cursor = set.upper_bound_mut(Bound::Unbounded);
    assert_eq!(cursor.peek_prev(), Some(&4));
    assert_eq!(cursor.peek_next(), None);

## Trait Implementations§

1.0.0 · Source§

### impl<T: Ord + Clone, A: Allocator + Clone> BitAnd<&BTreeSet<T, A>> for &BTreeSet<T, A>

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#### fn bitand(self, rhs: &BTreeSet<T, A>) -> 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]));

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#### type Output = BTreeSet<T, A>

The resulting type after applying the `&` operator.
1.0.0 · Source§

### impl<T: Ord + Clone, A: Allocator + Clone> BitOr<&BTreeSet<T, A>> for &BTreeSet<T, A>

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#### fn bitor(self, rhs: &BTreeSet<T, A>) -> 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]));

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#### type Output = BTreeSet<T, A>

The resulting type after applying the `|` operator.
1.0.0 · Source§

### impl<T: Ord + Clone, A: Allocator + Clone> BitXor<&BTreeSet<T, A>> for &BTreeSet<T, A>

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#### fn bitxor(self, rhs: &BTreeSet<T, A>) -> 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]));

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#### type Output = BTreeSet<T, A>

The resulting type after applying the `^` operator.
1.0.0 · Source§

### impl<T: Clone, A: Allocator + Clone> Clone for BTreeSet<T, A>

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#### fn clone(&self) -> Self

Returns a duplicate of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
1.0.0 · Source§

### impl<T: Debug, A: Allocator + Clone> Debug for BTreeSet<T, A>

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
1.0.0 · Source§

### impl<T> Default for BTreeSet<T>

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#### fn default() -> BTreeSet<T>

Creates an empty `BTreeSet`.

1.0.0 · Source§

### impl<T: Eq, A: Allocator + Clone> Eq for BTreeSet<T, A>

1.2.0 · Source§

### impl<'a, T: 'a + Ord + Copy, A: Allocator + Clone> Extend<&'a T> for BTreeSet<T, A>

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#### fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I)

Extends a collection with the contents of an iterator. Read more
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#### fn extend_one(&mut self, elem: &'a T)

🔬This is a nightly-only experimental API. (`extend_one` #72631)
Extends a collection with exactly one element.
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#### fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (`extend_one` #72631)
Reserves capacity in a collection for the given number of additional elements. Read more
1.0.0 · Source§

### impl<T: Ord, A: Allocator + Clone> Extend<T> for BTreeSet<T, A>

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#### fn extend<Iter: IntoIterator<Item = T>>(&mut self, iter: Iter)

Extends a collection with the contents of an iterator. Read more
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#### fn extend_one(&mut self, elem: T)

🔬This is a nightly-only experimental API. (`extend_one` #72631)
Extends a collection with exactly one element.
Source§

#### fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (`extend_one` #72631)
Reserves capacity in a collection for the given number of additional elements. Read more
1.56.0 · Source§

### impl<T: Ord, const N: usize> From<[T; N]> for BTreeSet<T>

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#### fn from(arr: [T; N]) -> Self

Converts a `[T; N]` into a `BTreeSet<T>`.

If the array contains any equal values, all but one will be dropped.

##### §Examples

    use std::collections::BTreeSet;

    let set1 = BTreeSet::from([1, 2, 3, 4]);
    let set2: BTreeSet<_> = [1, 2, 3, 4].into();
    assert_eq!(set1, set2);

1.0.0 · Source§

### impl<T: Ord> FromIterator<T> for BTreeSet<T>

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#### fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BTreeSet<T>

Creates a value from an iterator. Read more
1.0.0 · Source§

### impl<T: Hash, A: Allocator + Clone> Hash for BTreeSet<T, A>

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#### fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given `Hasher`. Read more
1.3.0 · Source§

#### fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given `Hasher`. Read more
1.0.0 · Source§

### impl<T, A: Allocator + Clone> IntoIterator for BTreeSet<T, A>

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#### fn into_iter(self) -> IntoIter<T, A> ⓘ

Gets an iterator for moving out the `BTreeSet`’s contents in ascending order.

##### §Examples

    use std::collections::BTreeSet;

    let set = BTreeSet::from([1, 2, 3, 4]);

    let v: Vec<_> = set.into_iter().collect();
    assert_eq!(v, [1, 2, 3, 4]);

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#### type Item = T

The type of the elements being iterated over.
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#### type IntoIter = IntoIter<T, A>

Which kind of iterator are we turning this into?
1.0.0 · Source§

### impl<'a, T, A: Allocator + Clone> IntoIterator for &'a BTreeSet<T, A>

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#### type Item = &'a T

The type of the elements being iterated over.
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#### type IntoIter = Iter<'a, T>

Which kind of iterator are we turning this into?
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#### fn into_iter(self) -> Iter<'a, T> ⓘ

Creates an iterator from a value. Read more
1.0.0 · Source§

### impl<T: Ord, A: Allocator + Clone> Ord for BTreeSet<T, A>

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#### fn cmp(&self, other: &BTreeSet<T, A>) -> Ordering

This method returns an `Ordering` between `self` and `other`. Read more
1.21.0 (const: unstable) · Source§

#### fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
1.21.0 (const: unstable) · Source§

#### fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
1.50.0 (const: unstable) · Source§

#### fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized,

Restrict a value to a certain interval. Read more
1.0.0 · Source§

### impl<T: PartialEq, A: Allocator + Clone> PartialEq for BTreeSet<T, A>

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#### fn eq(&self, other: &BTreeSet<T, A>) -> bool

Tests for `self` and `other` values to be equal, and is used by `==`.
1.0.0 (const: unstable) · Source§

#### fn ne(&self, other: &Rhs) -> bool

Tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
1.0.0 · Source§

### impl<T: PartialOrd, A: Allocator + Clone> PartialOrd for BTreeSet<T, A>

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#### fn partial_cmp(&self, other: &BTreeSet<T, A>) -> Option<Ordering>

This method returns an ordering between `self` and `other` values if one exists. Read more
1.0.0 (const: unstable) · Source§

#### fn lt(&self, other: &Rhs) -> bool

Tests less than (for `self` and `other`) and is used by the `<` operator. Read more
1.0.0 (const: unstable) · Source§

#### fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more
1.0.0 (const: unstable) · Source§

#### fn gt(&self, other: &Rhs) -> bool

Tests greater than (for `self` and `other`) and is used by the `>` operator. Read more
1.0.0 (const: unstable) · Source§

#### fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more
1.0.0 · Source§

### impl<T: Ord + Clone, A: Allocator + Clone> Sub<&BTreeSet<T, A>> for &BTreeSet<T, A>

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#### fn sub(self, rhs: &BTreeSet<T, A>) -> 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]));

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#### type Output = BTreeSet<T, A>

The resulting type after applying the `-` operator.

## Auto Trait Implementations§

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### impl<T, A> Freeze for BTreeSet<T, A>
where A: Freeze,

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### impl<T, A> RefUnwindSafe for BTreeSet<T, A>
where A: RefUnwindSafe, T: RefUnwindSafe,

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### impl<T, A> Send for BTreeSet<T, A>
where T: Send, A: Send,

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### impl<T, A> Sync for BTreeSet<T, A>
where T: Sync, A: Sync,

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### impl<T, A> Unpin for BTreeSet<T, A>
where A: Unpin,

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### impl<T, A> UnsafeUnpin for BTreeSet<T, A>
where A: UnsafeUnpin,

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### impl<T, A> UnwindSafe for BTreeSet<T, A>
where A: UnwindSafe, T: RefUnwindSafe,

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit` #126799)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.