## Cursor

# Struct Cursor

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    pub struct Cursor<'a, K: 'a> { /* private fields */ }

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

A cursor over a `BTreeSet`.

A `Cursor` is like an iterator, except that it can freely seek back-and-forth.

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

A `Cursor` is created with the `BTreeSet::lower_bound` and `BTreeSet::upper_bound` methods.

## Implementations§

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### impl<'a, K> Cursor<'a, K>

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#### pub fn next(&mut self) -> Option<&'a K>

🔬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.

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#### pub fn prev(&mut self) -> Option<&'a K>

🔬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.

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#### pub fn peek_next(&self) -> Option<&'a K>

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

Returns a reference to next element without moving the cursor.

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

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#### pub fn peek_prev(&self) -> Option<&'a K>

🔬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.

## Trait Implementations§

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### impl<'a, K: Clone + 'a> Clone for Cursor<'a, K>

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#### fn clone(&self) -> Cursor<'a, K>

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
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### impl<K: Debug> Debug for Cursor<'_, K>

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations§

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### impl<'a, K> Freeze for Cursor<'a, K>

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### impl<'a, K> RefUnwindSafe for Cursor<'a, K>
where K: RefUnwindSafe,

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### impl<'a, K> Send for Cursor<'a, K>
where K: Sync,

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### impl<'a, K> Sync for Cursor<'a, K>
where K: Sync,

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### impl<'a, K> Unpin for Cursor<'a, K>

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### impl<'a, K> UnwindSafe for Cursor<'a, K>
where K: 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.