Struct alloc::collections::btree_map::CursorMutKey

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

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

A cursor over a BTreeMap with editing operations, and which allows mutating the key of elements.

A Cursor is like an iterator, except that it can freely seek back-and-forth, and can safely mutate the map 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 map, and can operate on the two immediately adjacent elements.

A CursorMutKey is created from a CursorMut with the CursorMut::with_mutable_key method.

Safety

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

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

Implementations

impl<'a, K, V, A> CursorMutKey<'a, K, V, A>

pub fn next(&mut self) -> Option<(&mut K, &mut V)>

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

Advances the cursor to the next gap, returning the key and value of the element that it moved over.

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

pub fn prev(&mut self) -> Option<(&mut K, &mut V)>

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

Advances the cursor to the previous gap, returning the key and value of the element that it moved over.

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

pub fn peek_next(&mut self) -> Option<(&mut K, &mut V)>

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

Returns a reference to the the key and value of the next element without moving the cursor.

If the cursor is at the end of the map then None is returned

pub fn peek_prev(&mut self) -> Option<(&mut K, &mut V)>

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

Returns a reference to the the key and value of the previous element without moving the cursor.

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

pub fn as_cursor(&self) -> Cursor<'_, K, V>

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

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

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

impl<'a, K: Ord, V, A: Allocator + Clone> CursorMutKey<'a, K, V, A>

pub unsafe fn insert_after_unchecked(&mut self, key: K, value: V)

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

Inserts a new element into the BTreeMap in the gap that the CursorMutKey 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 BTreeMap invariants are maintained. Specifically:

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

pub unsafe fn insert_before_unchecked(&mut self, key: K, value: V)

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

Inserts a new element into the BTreeMap in the gap that the CursorMutKey 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 BTreeMap invariants are maintained. Specifically:

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

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

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

Inserts a new element into the BTreeMap in the gap that the CursorMutKey is currently pointing to.

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

Panics

This function panics if:

• the given key compares less than or equal to the current element (if any).
• the given key compares greater than or equal to the next element (if any).

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

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

Inserts a new element into the BTreeMap in the gap that the CursorMutKey is currently pointing to.

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

Panics

This function panics if:

• the given key compares greater than or equal to the current element (if any).
• the given key compares less than or equal to the previous element (if any).

pub fn remove_next(&mut self) -> Option<(K, V)>

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

Removes the next element from the BTreeMap.

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

pub fn remove_prev(&mut self) -> Option<(K, V)>

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

Removes the precending element from the BTreeMap.

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

Trait Implementations

impl<K: Debug, V: Debug, A> Debug for CursorMutKey<'_, K, V, A>

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

Formats the value using the given formatter.