Struct CursorMut

pub struct CursorMut<'a, K, A = Global>
where
    K: 'a,
{ /* private fields */ }

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

A cursor over a BTreeSet with editing operations.

A Cursor is like an iterator, except that it can freely seek back-and-forth, and can safely mutate the set during iteration. This is because the lifetime of its yielded references is tied to its own lifetime, instead of just the underlying map. This means cursors cannot yield multiple elements at once.

Cursors always point to a gap between two elements in the set, and can operate on the two immediately adjacent elements.

A CursorMut is created with the BTreeSet::lower_bound_mut and BTreeSet::upper_bound_mut methods.

Implementations

impl<'a, T, A> CursorMut<'a, T, A>

pub fn next(&mut self) -> Option<&T>

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

Advances the cursor to the next gap, returning the element that it moved over.

If the cursor is already at the end of the set then None is returned and the cursor is not moved.

pub fn prev(&mut self) -> Option<&T>

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

Advances the cursor to the previous gap, returning the element that it moved over.

If the cursor is already at the start of the set then None is returned and the cursor is not moved.

pub fn peek_next(&mut self) -> Option<&T>

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

Returns a reference to the next element without moving the cursor.

If the cursor is at the end of the set then None is returned.

pub fn peek_prev(&mut self) -> Option<&T>

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

Returns a reference to the previous element without moving the cursor.

If the cursor is at the start of the set then None is returned.

pub fn as_cursor(&self) -> Cursor<'_, T>

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

Returns a read-only cursor pointing to the same location as the CursorMut.

The lifetime of the returned Cursor is bound to that of the CursorMut, which means it cannot outlive the CursorMut and that the CursorMut is frozen for the lifetime of the Cursor.

pub unsafe fn with_mutable_key(self) -> CursorMutKey<'a, T, A>

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

Converts the cursor into a CursorMutKey, which allows mutating elements in the tree.

Safety

Since this cursor allows mutating elements, you must ensure that the BTreeSet invariants are maintained. Specifically:

• The newly inserted element must be unique in the tree.
• All elements in the tree must remain in sorted order.

impl<'a, T, A> CursorMut<'a, T, A>

where T: Ord, A: Allocator + Clone,

pub unsafe fn insert_after_unchecked(&mut self, value: T)

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

Inserts a new element into the set in the gap that the cursor is currently pointing to.

After the insertion the cursor will be pointing at the gap before the newly inserted element.

Safety

You must ensure that the BTreeSet invariants are maintained. Specifically:

• The newly inserted element must be unique in the tree.
• All elements in the tree must remain in sorted order.

pub unsafe fn insert_before_unchecked(&mut self, value: T)

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

Inserts a new element into the set in the gap that the cursor is currently pointing to.

After the insertion the cursor will be pointing at the gap after the newly inserted element.

Safety

You must ensure that the BTreeSet invariants are maintained. Specifically:

• The newly inserted element must be unique in the tree.
• All elements in the tree must remain in sorted order.

pub fn insert_after(&mut self, value: T) -> Result<(), UnorderedKeyError>

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

Inserts a new element into the set in the gap that the cursor is currently pointing to.

After the insertion the cursor will be pointing at the gap before the newly inserted element.

If the inserted element is not greater than the element before the cursor (if any), or if it not less than the element after the cursor (if any), then an UnorderedKeyError is returned since this would invalidate the Ord invariant between the elements of the set.

pub fn insert_before(&mut self, value: T) -> Result<(), UnorderedKeyError>

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

Inserts a new element into the set in the gap that the cursor is currently pointing to.

After the insertion the cursor will be pointing at the gap after the newly inserted element.

If the inserted element is not greater than the element before the cursor (if any), or if it not less than the element after the cursor (if any), then an UnorderedKeyError is returned since this would invalidate the Ord invariant between the elements of the set.

pub fn remove_next(&mut self) -> Option<T>

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

Removes the next element from the BTreeSet.

The element that was removed is returned. The cursor position is unchanged (before the removed element).

pub fn remove_prev(&mut self) -> Option<T>

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

Removes the preceding element from the BTreeSet.

The element that was removed is returned. The cursor position is unchanged (after the removed element).

Trait Implementations

impl<K, A> Debug for CursorMut<'_, K, A>

where K: Debug,

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

Formats the value using the given formatter.