# Struct indexmap::set::IndexSet [−] [src]

    pub struct IndexSet<T, S = RandomState> { /* fields omitted */ }

A hash set where the iteration order of the values is independent of their hash values.

The interface is closely compatible with the standard `HashSet`, but also has additional features.

# Order

The values have a consistent order that is determined by the sequence of insertion and removal calls on the set. The order does not depend on the values or the hash function at all. Note that insertion order and value are not affected if a re-insertion is attempted once an element is already present.

All iterators traverse the set in order. Set operation iterators like `union` produce a concatenated order, as do their matching “bitwise” operators. See their documentation for specifics.

The insertion order is preserved, with notable exceptions like the `.remove()` or `.swap_remove()` methods. Methods such as `.sort_by()` of course result in a new order, depending on the sorting order.

# Indices

The values are indexed in a compact range without holes in the range `0..self.len()`. For example, the method `.get_full` looks up the index for a value, and the method `.get_index` looks up the value by index.

# Examples

    use indexmap::IndexSet;

    // Collects which letters appear in a sentence.
    let letters: IndexSet<_> = "a short treatise on fungi".chars().collect();

    assert!(letters.contains(&'s'));
    assert!(letters.contains(&'t'));
    assert!(letters.contains(&'u'));
    assert!(!letters.contains(&'y'));

## Implementations

### `impl<T> IndexSet<T>` [src]

#### `pub fn new() -> Self` [src]

Create a new set. (Does not allocate.)

#### `pub fn with_capacity(n: usize) -> Self` [src]

Create a new set with capacity for `n` elements. (Does not allocate if `n` is zero.)

Computes in O(n) time.

### `impl<T, S> IndexSet<T, S>` [src]

#### `pub fn with_capacity_and_hasher(n: usize, hash_builder: S) -> Self` [src]

Create a new set with capacity for `n` elements. (Does not allocate if `n` is zero.)

Computes in O(n) time.

#### `pub fn with_hasher(hash_builder: S) -> Self` [src]

Create a new set with `hash_builder`

#### `pub fn capacity(&self) -> usize` [src]

Computes in O(1) time.

#### `pub fn hasher(&self) -> &S` [src]

Return a reference to the set’s `BuildHasher`.

#### `pub fn len(&self) -> usize` [src]

Return the number of elements in the set.

Computes in O(1) time.

#### `pub fn is_empty(&self) -> bool` [src]

Returns true if the set contains no elements.

Computes in O(1) time.

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

### Notable traits for Iter<'a, T>

`impl<'a, T> Iterator for Iter<'a, T> type Item = &'a T;`
` [src]

Return an iterator over the values of the set, in their order

#### `pub fn clear(&mut self)` [src]

Remove all elements in the set, while preserving its capacity.

Computes in O(n) time.

#### `pub fn truncate(&mut self, len: usize)` [src]

Shortens the set, keeping the first `len` elements and dropping the rest.

If `len` is greater than the set’s current length, this has no effect.

#### `pub fn drain<R>(&mut self, range: R) -> Drain<'_, T>ⓘ

### Notable traits for Drain<'_, T>

`impl<T> Iterator for Drain<'_, T> type Item = T;`
where
R: RangeBounds<usize>,` [src]

Clears the `IndexSet` in the given index range, returning those values as a drain iterator.

The range may be any type that implements `RangeBounds<usize>`, including all of the `std::ops::Range*` types, or even a tuple pair of `Bound` start and end values. To drain the set entirely, use `RangeFull` like `set.drain(..)`.

This shifts down all entries following the drained range to fill the gap, and keeps the allocated memory for reuse.

Panics if the starting point is greater than the end point or if the end point is greater than the length of the set.

#### `pub fn split_off(&mut self, at: usize) -> Self where
S: Clone,` [src]

Splits the collection into two at the given index.

Returns a newly allocated set containing the elements in the range `[at, len)`. After the call, the original set will be left containing the elements `[0, at)` with its previous capacity unchanged.

Panics if `at > len`.

### `impl<T, S> IndexSet<T, S> where
T: Hash + Eq,
S: BuildHasher,` [src]

#### `pub fn reserve(&mut self, additional: usize)` [src]

Reserve capacity for `additional` more values.

Computes in O(n) time.

#### `pub fn shrink_to_fit(&mut self)` [src]

Shrink the capacity of the set as much as possible.

Computes in O(n) time.

#### `pub fn insert(&mut self, value: T) -> bool` [src]

Insert the value into the set.

If an equivalent item already exists in the set, it returns `false` leaving the original value in the set and without altering its insertion order. Otherwise, it inserts the new item and returns `true`.

Computes in O(1) time (amortized average).

#### `pub fn insert_full(&mut self, value: T) -> (usize, bool)` [src]

Insert the value into the set, and get its index.

If an equivalent item already exists in the set, it returns the index of the existing item and `false`, leaving the original value in the set and without altering its insertion order. Otherwise, it inserts the new item and returns the index of the inserted item and `true`.

Computes in O(1) time (amortized average).

#### `pub fn difference<'a, S2>(
&'a self,
other: &'a IndexSet<T, S2>
) -> Difference<'a, T, S2>ⓘ

### Notable traits for Difference<'a, T, S>

`impl<'a, T, S> Iterator for Difference<'a, T, S> where
T: Eq + Hash,
S: BuildHasher, type Item = &'a T;`
where
S2: BuildHasher,` [src]

Return an iterator over the values that are in `self` but not `other`.

Values are produced in the same order that they appear in `self`.

#### `pub fn symmetric_difference<'a, S2>(
&'a self,
other: &'a IndexSet<T, S2>
) -> SymmetricDifference<'a, T, S, S2>ⓘ

### Notable traits for SymmetricDifference<'a, T, S1, S2>

`impl<'a, T, S1, S2> Iterator for SymmetricDifference<'a, T, S1, S2> where
T: Eq + Hash,
S1: BuildHasher,
S2: BuildHasher, type Item = &'a T;`
where
S2: BuildHasher,` [src]

Return an iterator over the values that are in `self` or `other`, but not in both.

Values from `self` are produced in their original order, followed by values from `other` in their original order.

#### `pub fn intersection<'a, S2>(
&'a self,
other: &'a IndexSet<T, S2>
) -> Intersection<'a, T, S2>ⓘ

### Notable traits for Intersection<'a, T, S>

`impl<'a, T, S> Iterator for Intersection<'a, T, S> where
T: Eq + Hash,
S: BuildHasher, type Item = &'a T;`
where
S2: BuildHasher,` [src]

Return an iterator over the values that are in both `self` and `other`.

Values are produced in the same order that they appear in `self`.

#### `pub fn union<'a, S2>(&'a self, other: &'a IndexSet<T, S2>) -> Union<'a, T, S>ⓘ

### Notable traits for Union<'a, T, S>

`impl<'a, T, S> Iterator for Union<'a, T, S> where
T: Eq + Hash,
S: BuildHasher, type Item = &'a T;`
where
S2: BuildHasher,` [src]

Return an iterator over all values that are in `self` or `other`.

Values from `self` are produced in their original order, followed by values that are unique to `other` in their original order.

#### `pub fn contains<Q: ?Sized>(&self, value: &Q) -> bool where
Q: Hash + Equivalent<T>,` [src]

Return `true` if an equivalent to `value` exists in the set.

Computes in O(1) time (average).

#### `pub fn get<Q: ?Sized>(&self, value: &Q) -> Option<&T> where
Q: Hash + Equivalent<T>,` [src]

Return a reference to the value stored in the set, if it is present, else `None`.

Computes in O(1) time (average).

#### `pub fn get_full<Q: ?Sized>(&self, value: &Q) -> Option<(usize, &T)> where
Q: Hash + Equivalent<T>,` [src]

Return item index and value

#### `pub fn get_index_of<Q: ?Sized>(&self, value: &Q) -> Option<usize> where
Q: Hash + Equivalent<T>,` [src]

Return item index, if it exists in the set

#### `pub fn replace(&mut self, value: T) -> Option<T>` [src]

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

Computes in O(1) time (average).

#### `pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool where
Q: Hash + Equivalent<T>,` [src]

Remove the value from the set, and return `true` if it was present.

NOTE: This is equivalent to `.swap_remove(value)`, if you want to preserve the order of the values in the set, use `.shift_remove(value)`.

Computes in O(1) time (average).

#### `pub fn swap_remove<Q: ?Sized>(&mut self, value: &Q) -> bool where
Q: Hash + Equivalent<T>,` [src]

Remove the value from the set, and return `true` if it was present.

Like `Vec::swap_remove`, the value is removed by swapping it with the last element of the set and popping it off. This perturbs the position of what used to be the last element!

Return `false` if `value` was not in the set.

Computes in O(1) time (average).

#### `pub fn shift_remove<Q: ?Sized>(&mut self, value: &Q) -> bool where
Q: Hash + Equivalent<T>,` [src]

Remove the value from the set, and return `true` if it was present.

Like `Vec::remove`, the value is removed by shifting all of the elements that follow it, preserving their relative order. This perturbs the index of all of those elements!

Return `false` if `value` was not in the set.

Computes in O(n) time (average).

#### `pub fn take<Q: ?Sized>(&mut self, value: &Q) -> Option<T> where
Q: Hash + Equivalent<T>,` [src]

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

NOTE: This is equivalent to `.swap_take(value)`, if you need to preserve the order of the values in the set, use `.shift_take(value)` instead.

Computes in O(1) time (average).

#### `pub fn swap_take<Q: ?Sized>(&mut self, value: &Q) -> Option<T> where
Q: Hash + Equivalent<T>,` [src]

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

Like `Vec::swap_remove`, the value is removed by swapping it with the last element of the set and popping it off. This perturbs the position of what used to be the last element!

Return `None` if `value` was not in the set.

Computes in O(1) time (average).

#### `pub fn shift_take<Q: ?Sized>(&mut self, value: &Q) -> Option<T> where
Q: Hash + Equivalent<T>,` [src]

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

Like `Vec::remove`, the value is removed by shifting all of the elements that follow it, preserving their relative order. This perturbs the index of all of those elements!

Return `None` if `value` was not in the set.

Computes in O(n) time (average).

#### `pub fn swap_remove_full<Q: ?Sized>(&mut self, value: &Q) -> Option<(usize, T)> where
Q: Hash + Equivalent<T>,` [src]

Remove the value from the set return it and the index it had.

Like `Vec::swap_remove`, the value is removed by swapping it with the last element of the set and popping it off. This perturbs the position of what used to be the last element!

Return `None` if `value` was not in the set.

#### `pub fn shift_remove_full<Q: ?Sized>(&mut self, value: &Q) -> Option<(usize, T)> where
Q: Hash + Equivalent<T>,` [src]

Remove the value from the set return it and the index it had.

Like `Vec::remove`, the value is removed by shifting all of the elements that follow it, preserving their relative order. This perturbs the index of all of those elements!

Return `None` if `value` was not in the set.

#### `pub fn pop(&mut self) -> Option<T>` [src]

Remove the last value

Computes in O(1) time (average).

#### `pub fn retain<F>(&mut self, keep: F) where
F: FnMut(&T) -> bool,` [src]

Scan through each value in the set and keep those where the closure `keep` returns `true`.

The elements are visited in order, and remaining elements keep their order.

Computes in O(n) time (average).

#### `pub fn sort(&mut self) where
T: Ord,` [src]

Sort the set’s values by their default ordering.

See `sort_by` for details.

#### `pub fn sort_by<F>(&mut self, compare: F) where
F: FnMut(&T, &T) -> Ordering,` [src]

Sort the set’s values in place using the comparison function `compare`.

Computes in O(n log n) time and O(n) space. The sort is stable.

#### `pub fn sorted_by<F>(self, cmp: F) -> IntoIter<T>ⓘ

### Notable traits for IntoIter<T>

`impl<T> Iterator for IntoIter<T> type Item = T;`
where
F: FnMut(&T, &T) -> Ordering,` [src]

Sort the values of the set and return a by value iterator of the values with the result.

The sort is stable.

#### `pub fn reverse(&mut self)` [src]

Reverses the order of the set’s values in place.

Computes in O(n) time and O(1) space.

### `impl<T, S> IndexSet<T, S>` [src]

#### `pub fn get_index(&self, index: usize) -> Option<&T>` [src]

Get a value by index

Valid indices are 0 <= index < self.len()

Computes in O(1) time.

#### `pub fn first(&self) -> Option<&T>` [src]

Get the first value

Computes in O(1) time.

#### `pub fn last(&self) -> Option<&T>` [src]

Get the last value

Computes in O(1) time.

#### `pub fn swap_remove_index(&mut self, index: usize) -> Option<T>` [src]

Remove the value by index

Valid indices are 0 <= index < self.len()

Like `Vec::swap_remove`, the value is removed by swapping it with the last element of the set and popping it off. This perturbs the position of what used to be the last element!

Computes in O(1) time (average).

#### `pub fn shift_remove_index(&mut self, index: usize) -> Option<T>` [src]

Remove the value by index

Valid indices are 0 <= index < self.len()

Like `Vec::remove`, the value is removed by shifting all of the elements that follow it, preserving their relative order. This perturbs the index of all of those elements!

Computes in O(n) time (average).

#### `pub fn swap_indices(&mut self, a: usize, b: usize)` [src]

Swaps the position of two values in the set.

Panics if `a` or `b` are out of bounds.

### `impl<T, S> IndexSet<T, S> where
T: Eq + Hash,
S: BuildHasher,` [src]

#### `pub fn is_disjoint<S2>(&self, other: &IndexSet<T, S2>) -> bool where
S2: BuildHasher,` [src]

Returns `true` if `self` has no elements in common with `other`.

#### `pub fn is_subset<S2>(&self, other: &IndexSet<T, S2>) -> bool where
S2: BuildHasher,` [src]

Returns `true` if all elements of `self` are contained in `other`.

#### `pub fn is_superset<S2>(&self, other: &IndexSet<T, S2>) -> bool where
S2: BuildHasher,` [src]

Returns `true` if all elements of `other` are contained in `self`.

## Trait Implementations

### `impl<T, S1, S2> BitAnd<&'_ IndexSet<T, S2>> for &IndexSet<T, S1> where
T: Eq + Hash + Clone,
S1: BuildHasher + Default,
S2: BuildHasher,` [src]

#### `type Output = IndexSet<T, S1>`

The resulting type after applying the `&` operator.

#### `fn bitand(self, other: &IndexSet<T, S2>) -> Self::Output` [src]

Returns the set intersection, cloned into a new set.

Values are collected in the same order that they appear in `self`.

### `impl<T, S1, S2> BitOr<&'_ IndexSet<T, S2>> for &IndexSet<T, S1> where
T: Eq + Hash + Clone,
S1: BuildHasher + Default,
S2: BuildHasher,` [src]

#### `type Output = IndexSet<T, S1>`

The resulting type after applying the `|` operator.

#### `fn bitor(self, other: &IndexSet<T, S2>) -> Self::Output` [src]

Returns the set union, cloned into a new set.

Values from `self` are collected in their original order, followed by values that are unique to `other` in their original order.

### `impl<T, S1, S2> BitXor<&'_ IndexSet<T, S2>> for &IndexSet<T, S1> where
T: Eq + Hash + Clone,
S1: BuildHasher + Default,
S2: BuildHasher,` [src]

#### `type Output = IndexSet<T, S1>`

The resulting type after applying the `^` operator.

#### `fn bitxor(self, other: &IndexSet<T, S2>) -> Self::Output` [src]

Returns the set symmetric-difference, cloned into a new set.

Values from `self` are collected in their original order, followed by values from `other` in their original order.

### `impl<T, S> Clone for IndexSet<T, S> where
T: Clone,
S: Clone,` [src]

#### `fn clone(&self) -> Self` [src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, other: &Self)` [src]

Performs copy-assignment from `source`. Read more

### `impl<T, S> Debug for IndexSet<T, S> where
T: Debug,` [src]

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

Formats the value using the given formatter. Read more

### `impl<T, S> Default for IndexSet<T, S> where
S: Default,` [src]

#### `fn default() -> Self` [src]

Return an empty `IndexSet`

### `impl<T, S> Eq for IndexSet<T, S> where
T: Eq + Hash,
S: BuildHasher,` [src]

### `impl<'a, T, S> Extend<&'a T> for IndexSet<T, S> where
T: Hash + Eq + Copy + 'a,
S: BuildHasher,` [src]

#### `fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iterable: I)` [src]

Extends a collection with the contents of an iterator. Read more

#### `pub fn extend_one(&mut self, item: A)` [src]

🔬 This is a nightly-only experimental API. (`extend_one`)

Extends a collection with exactly one element.

#### `pub fn extend_reserve(&mut self, additional: usize)` [src]

🔬 This is a nightly-only experimental API. (`extend_one`)

Reserves capacity in a collection for the given number of additional elements. Read more

### `impl<T, S> Extend<T> for IndexSet<T, S> where
T: Hash + Eq,
S: BuildHasher,` [src]

#### `fn extend<I: IntoIterator<Item = T>>(&mut self, iterable: I)` [src]

Extends a collection with the contents of an iterator. Read more

#### `pub fn extend_one(&mut self, item: A)` [src]

🔬 This is a nightly-only experimental API. (`extend_one`)

Extends a collection with exactly one element.

#### `pub fn extend_reserve(&mut self, additional: usize)` [src]

🔬 This is a nightly-only experimental API. (`extend_one`)

Reserves capacity in a collection for the given number of additional elements. Read more

### `impl<T, S> FromIterator<T> for IndexSet<T, S> where
T: Hash + Eq,
S: BuildHasher + Default,` [src]

#### `fn from_iter<I: IntoIterator<Item = T>>(iterable: I) -> Self` [src]

Creates a value from an iterator. Read more

### `impl<T, S> Index<usize> for IndexSet<T, S>` [src]

Access `IndexSet` values at indexed positions.

# Examples

    use indexmap::IndexSet;

    let mut set = IndexSet::new();
    for word in "Lorem ipsum dolor sit amet".split_whitespace() {
        set.insert(word.to_string());
    }
    assert_eq!(set[0], "Lorem");
    assert_eq!(set[1], "ipsum");
    set.reverse();
    assert_eq!(set[0], "amet");
    assert_eq!(set[1], "sit");
    set.sort();
    assert_eq!(set[0], "Lorem");
    assert_eq!(set[1], "amet");

ⓘ

    use indexmap::IndexSet;

    let mut set = IndexSet::new();
    set.insert("foo");
    println!("{:?}", set[10]); // panics!

#### `type Output = T`

The returned type after indexing.

#### `fn index(&self, index: usize) -> &T` [src]

Returns a reference to the value at the supplied `index`.

Panics if `index` is out of bounds.

### `impl<'a, T, S> IntoIterator for &'a IndexSet<T, S>` [src]

#### `type Item = &'a T`

The type of the elements being iterated over.

#### `type IntoIter = Iter<'a, T>`

Which kind of iterator are we turning this into?

#### `fn into_iter(self) -> Self::IntoIter` [src]

Creates an iterator from a value. Read more

### `impl<T, S> IntoIterator for IndexSet<T, S>` [src]

#### `type Item = T`

The type of the elements being iterated over.

#### `type IntoIter = IntoIter<T>`

Which kind of iterator are we turning this into?

#### `fn into_iter(self) -> Self::IntoIter` [src]

Creates an iterator from a value. Read more

### `impl<T, S1, S2> PartialEq<IndexSet<T, S2>> for IndexSet<T, S1> where
T: Hash + Eq,
S1: BuildHasher,
S2: BuildHasher,` [src]

#### `fn eq(&self, other: &IndexSet<T, S2>) -> bool` [src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `#[must_use]pub fn ne(&self, other: &Rhs) -> bool` 1.0.0 [src]

This method tests for `!=`.

### `impl<T, S1, S2> Sub<&'_ IndexSet<T, S2>> for &IndexSet<T, S1> where
T: Eq + Hash + Clone,
S1: BuildHasher + Default,
S2: BuildHasher,` [src]

#### `type Output = IndexSet<T, S1>`

The resulting type after applying the `-` operator.

#### `fn sub(self, other: &IndexSet<T, S2>) -> Self::Output` [src]

Returns the set difference, cloned into a new set.

Values are collected in the same order that they appear in `self`.

## Auto Trait Implementations

### `impl<T, S> RefUnwindSafe for IndexSet<T, S> where
S: RefUnwindSafe,
T: RefUnwindSafe,`

### `impl<T, S> Send for IndexSet<T, S> where
S: Send,
T: Send,`

### `impl<T, S> Sync for IndexSet<T, S> where
S: Sync,
T: Sync,`

### `impl<T, S> Unpin for IndexSet<T, S> where
S: Unpin,
T: Unpin,`

### `impl<T, S> UnwindSafe for IndexSet<T, S> where
S: UnwindSafe,
T: UnwindSafe,`

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `pub fn type_id(&self) -> TypeId` [src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow(&self) -> &T` [src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow_mut(&mut self) -> &mut T` [src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T` [src]

#### `pub fn from(t: T) -> T` [src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `pub fn into(self) -> U` [src]

Performs the conversion.

### `impl<T> ToOwned for T where
T: Clone,` [src]

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `pub fn to_owned(&self) -> T` [src]

Creates owned data from borrowed data, usually by cloning. Read more

#### `pub fn clone_into(&self, target: &mut T)` [src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into`)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>` [src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

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

The type returned in the event of a conversion error.

#### `pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>` [src]

Performs the conversion.