Struct IndexMap

struct IndexMap<K, V, S = std::collections::hash_map::RandomState> { ... }

A hash table where the iteration order of the key-value pairs is independent of the hash values of the keys.

The interface is closely compatible with the standard [HashMap][std::collections::HashMap], but also has additional features.

Order

The key-value pairs have a consistent order that is determined by the sequence of insertion and removal calls on the map. The order does not depend on the keys or the hash function at all.

All iterators traverse the map in the order.

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

Indices

The key-value pairs 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 key, and the method .get_index looks up the key-value pair by index.

Examples

use indexmap::IndexMap;

// count the frequency of each letter in a sentence.
let mut letters = IndexMap::new();
for ch in "a short treatise on fungi".chars() {
    *letters.entry(ch).or_insert(0) += 1;
}

assert_eq!(letters[&'s'], 2);
assert_eq!(letters[&'t'], 3);
assert_eq!(letters[&'u'], 1);
assert_eq!(letters.get(&'y'), None);

Implementations

impl<K, V> IndexMap<K, V>

fn new() -> Self

Create a new map. (Does not allocate.)

fn with_capacity(n: usize) -> Self

Create a new map with capacity for n key-value pairs. (Does not allocate if n is zero.)

Computes in O(n) time.

impl<K, V, S> IndexMap<K, V, S>

fn insert(self: &mut Self, key: K, value: V) -> Option<V>

Insert a key-value pair in the map.

If an equivalent key already exists in the map: the key remains and retains in its place in the order, its corresponding value is updated with value, and the older value is returned inside Some(_).

If no equivalent key existed in the map: the new key-value pair is inserted, last in order, and None is returned.

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

See also [entry][Self::entry] if you want to insert or modify, or [insert_full][Self::insert_full] if you need to get the index of the corresponding key-value pair.

fn insert_full(self: &mut Self, key: K, value: V) -> (usize, Option<V>)

Insert a key-value pair in the map, and get their index.

If an equivalent key already exists in the map: the key remains and retains in its place in the order, its corresponding value is updated with value, and the older value is returned inside (index, Some(_)).

If no equivalent key existed in the map: the new key-value pair is inserted, last in order, and (index, None) is returned.

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

See also [entry][Self::entry] if you want to insert or modify.

fn insert_sorted(self: &mut Self, key: K, value: V) -> (usize, Option<V>)
where
    K: Ord

Insert a key-value pair in the map at its ordered position among sorted keys.

This is equivalent to finding the position with [binary_search_keys][Self::binary_search_keys], then either updating it or calling [insert_before][Self::insert_before] for a new key.

If the sorted key is found in the map, its corresponding value is updated with value, and the older value is returned inside (index, Some(_)). Otherwise, the new key-value pair is inserted at the sorted position, and (index, None) is returned.

If the existing keys are not already sorted, then the insertion index is unspecified (like slice::binary_search), but the key-value pair is moved to or inserted at that position regardless.

Computes in O(n) time (average). Instead of repeating calls to insert_sorted, it may be faster to call batched [insert][Self::insert] or [extend][Self::extend] and only call [sort_keys][Self::sort_keys] or [sort_unstable_keys][Self::sort_unstable_keys] once.

fn insert_before(self: &mut Self, index: usize, key: K, value: V) -> (usize, Option<V>)

Insert a key-value pair in the map before the entry at the given index, or at the end.

If an equivalent key already exists in the map: the key remains and is moved to the new position in the map, its corresponding value is updated with value, and the older value is returned inside Some(_). The returned index will either be the given index or one less, depending on how the entry moved. (See shift_insert for different behavior here.)

If no equivalent key existed in the map: the new key-value pair is inserted exactly at the given index, and None is returned.

Panics if index is out of bounds. Valid indices are 0..=map.len() (inclusive).

Computes in O(n) time (average).

See also [entry][Self::entry] if you want to insert or modify, perhaps only using the index for new entries with VacantEntry::shift_insert.

Examples

use indexmap::IndexMap;
let mut map: IndexMap<char, ()> = ('a'..='z').map(|c| (c, ())).collect();

// The new key '*' goes exactly at the given index.
assert_eq!(map.get_index_of(&'*'), None);
assert_eq!(map.insert_before(10, '*', ()), (10, None));
assert_eq!(map.get_index_of(&'*'), Some(10));

// Moving the key 'a' up will shift others down, so this moves *before* 10 to index 9.
assert_eq!(map.insert_before(10, 'a', ()), (9, Some(())));
assert_eq!(map.get_index_of(&'a'), Some(9));
assert_eq!(map.get_index_of(&'*'), Some(10));

// Moving the key 'z' down will shift others up, so this moves to exactly 10.
assert_eq!(map.insert_before(10, 'z', ()), (10, Some(())));
assert_eq!(map.get_index_of(&'z'), Some(10));
assert_eq!(map.get_index_of(&'*'), Some(11));

// Moving or inserting before the endpoint is also valid.
assert_eq!(map.len(), 27);
assert_eq!(map.insert_before(map.len(), '*', ()), (26, Some(())));
assert_eq!(map.get_index_of(&'*'), Some(26));
assert_eq!(map.insert_before(map.len(), '+', ()), (27, None));
assert_eq!(map.get_index_of(&'+'), Some(27));
assert_eq!(map.len(), 28);

fn shift_insert(self: &mut Self, index: usize, key: K, value: V) -> Option<V>

Insert a key-value pair in the map at the given index.

If an equivalent key already exists in the map: the key remains and is moved to the given index in the map, its corresponding value is updated with value, and the older value is returned inside Some(_). Note that existing entries cannot be moved to index == map.len()! (See insert_before for different behavior here.)

If no equivalent key existed in the map: the new key-value pair is inserted at the given index, and None is returned.

Panics if index is out of bounds. Valid indices are 0..map.len() (exclusive) when moving an existing entry, or 0..=map.len() (inclusive) when inserting a new key.

Computes in O(n) time (average).

See also [entry][Self::entry] if you want to insert or modify, perhaps only using the index for new entries with VacantEntry::shift_insert.

Examples

use indexmap::IndexMap;
let mut map: IndexMap<char, ()> = ('a'..='z').map(|c| (c, ())).collect();

// The new key '*' goes exactly at the given index.
assert_eq!(map.get_index_of(&'*'), None);
assert_eq!(map.shift_insert(10, '*', ()), None);
assert_eq!(map.get_index_of(&'*'), Some(10));

// Moving the key 'a' up to 10 will shift others down, including the '*' that was at 10.
assert_eq!(map.shift_insert(10, 'a', ()), Some(()));
assert_eq!(map.get_index_of(&'a'), Some(10));
assert_eq!(map.get_index_of(&'*'), Some(9));

// Moving the key 'z' down to 9 will shift others up, including the '*' that was at 9.
assert_eq!(map.shift_insert(9, 'z', ()), Some(()));
assert_eq!(map.get_index_of(&'z'), Some(9));
assert_eq!(map.get_index_of(&'*'), Some(10));

// Existing keys can move to len-1 at most, but new keys can insert at the endpoint.
assert_eq!(map.len(), 27);
assert_eq!(map.shift_insert(map.len() - 1, '*', ()), Some(()));
assert_eq!(map.get_index_of(&'*'), Some(26));
assert_eq!(map.shift_insert(map.len(), '+', ()), None);
assert_eq!(map.get_index_of(&'+'), Some(27));
assert_eq!(map.len(), 28);

use indexmap::IndexMap;
let mut map: IndexMap<char, ()> = ('a'..='z').map(|c| (c, ())).collect();

// This is an invalid index for moving an existing key!
map.shift_insert(map.len(), 'a', ());

fn entry(self: &mut Self, key: K) -> Entry<'_, K, V>

Get the given key’s corresponding entry in the map for insertion and/or in-place manipulation.

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

fn splice<R, I>(self: &mut Self, range: R, replace_with: I) -> Splice<'_, <I as >::IntoIter, K, V, S>
where
    R: RangeBounds<usize>,
    I: IntoIterator<Item = (K, V)>

Creates a splicing iterator that replaces the specified range in the map with the given replace_with key-value iterator and yields the removed items. replace_with does not need to be the same length as range.

The range is removed even if the iterator is not consumed until the end. It is unspecified how many elements are removed from the map if the Splice value is leaked.

The input iterator replace_with is only consumed when the Splice value is dropped. If a key from the iterator matches an existing entry in the map (outside of range), then the value will be updated in that position. Otherwise, the new key-value pair will be inserted in the replaced range.

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

Examples

use indexmap::IndexMap;

let mut map = IndexMap::from([(0, '_'), (1, 'a'), (2, 'b'), (3, 'c'), (4, 'd')]);
let new = [(5, 'E'), (4, 'D'), (3, 'C'), (2, 'B'), (1, 'A')];
let removed: Vec<_> = map.splice(2..4, new).collect();

// 1 and 4 got new values, while 5, 3, and 2 were newly inserted.
assert!(map.into_iter().eq([(0, '_'), (1, 'A'), (5, 'E'), (3, 'C'), (2, 'B'), (4, 'D')]));
assert_eq!(removed, &[(2, 'b'), (3, 'c')]);

fn append<S2>(self: &mut Self, other: &mut IndexMap<K, V, S2>)

Moves all key-value pairs from other into self, leaving other empty.

This is equivalent to calling [insert][Self::insert] for each key-value pair from other in order, which means that for keys that already exist in self, their value is updated in the current position.

Examples

use indexmap::IndexMap;

// Note: Key (3) is present in both maps.
let mut a = IndexMap::from([(3, "c"), (2, "b"), (1, "a")]);
let mut b = IndexMap::from([(3, "d"), (4, "e"), (5, "f")]);
let old_capacity = b.capacity();

a.append(&mut b);

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

assert!(a.keys().eq(&[3, 2, 1, 4, 5]));
assert_eq!(a[&3], "d"); // "c" was overwritten.

impl<K, V, S> IndexMap<K, V, S>

fn pop(self: &mut Self) -> Option<(K, V)>

Remove the last key-value pair

This preserves the order of the remaining elements.

Computes in O(1) time (average).

fn retain<F>(self: &mut Self, keep: F)
where
    F: FnMut(&K, &mut V) -> bool

Scan through each key-value pair in the map 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).

fn sort_keys(self: &mut Self)
where
    K: Ord

Sort the map’s key-value pairs by the default ordering of the keys.

This is a stable sort -- but equivalent keys should not normally coexist in a map at all, so [sort_unstable_keys][Self::sort_unstable_keys] is preferred because it is generally faster and doesn't allocate auxiliary memory.

See sort_by for details.

fn sort_by<F>(self: &mut Self, cmp: F)
where
    F: FnMut(&K, &V, &K, &V) -> Ordering

Sort the map’s key-value pairs in place using the comparison function cmp.

The comparison function receives two key and value pairs to compare (you can sort by keys or values or their combination as needed).

Computes in O(n log n + c) time and O(n) space where n is the length of the map and c the capacity. The sort is stable.

fn sorted_by<F>(self: Self, cmp: F) -> IntoIter<K, V>
where
    F: FnMut(&K, &V, &K, &V) -> Ordering

Sort the key-value pairs of the map and return a by-value iterator of the key-value pairs with the result.

The sort is stable.

fn sort_unstable_keys(self: &mut Self)
where
    K: Ord

Sort the map's key-value pairs by the default ordering of the keys, but may not preserve the order of equal elements.

See sort_unstable_by for details.

fn sort_unstable_by<F>(self: &mut Self, cmp: F)
where
    F: FnMut(&K, &V, &K, &V) -> Ordering

Sort the map's key-value pairs in place using the comparison function cmp, but may not preserve the order of equal elements.

The comparison function receives two key and value pairs to compare (you can sort by keys or values or their combination as needed).

Computes in O(n log n + c) time where n is the length of the map and c is the capacity. The sort is unstable.

fn sorted_unstable_by<F>(self: Self, cmp: F) -> IntoIter<K, V>
where
    F: FnMut(&K, &V, &K, &V) -> Ordering

Sort the key-value pairs of the map and return a by-value iterator of the key-value pairs with the result.

The sort is unstable.

fn sort_by_cached_key<T, F>(self: &mut Self, sort_key: F)
where
    T: Ord,
    F: FnMut(&K, &V) -> T

Sort the map’s key-value pairs in place using a sort-key extraction function.

During sorting, the function is called at most once per entry, by using temporary storage to remember the results of its evaluation. The order of calls to the function is unspecified and may change between versions of indexmap or the standard library.

Computes in O(m n + n log n + c) time () and O(n) space, where the function is O(m), n is the length of the map, and c the capacity. The sort is stable.

fn binary_search_keys(self: &Self, x: &K) -> Result<usize, usize>
where
    K: Ord

Search over a sorted map for a key.

Returns the position where that key is present, or the position where it can be inserted to maintain the sort. See slice::binary_search for more details.

Computes in O(log(n)) time, which is notably less scalable than looking the key up using [get_index_of][IndexMap::get_index_of], but this can also position missing keys.

fn binary_search_by<'a, F>(self: &'a Self, f: F) -> Result<usize, usize>
where
    F: FnMut(&'a K, &'a V) -> Ordering

Search over a sorted map with a comparator function.

Returns the position where that value is present, or the position where it can be inserted to maintain the sort. See slice::binary_search_by for more details.

Computes in O(log(n)) time.

fn binary_search_by_key<'a, B, F>(self: &'a Self, b: &B, f: F) -> Result<usize, usize>
where
    F: FnMut(&'a K, &'a V) -> B,
    B: Ord

Search over a sorted map with an extraction function.

Returns the position where that value is present, or the position where it can be inserted to maintain the sort. See slice::binary_search_by_key for more details.

Computes in O(log(n)) time.

fn partition_point<P>(self: &Self, pred: P) -> usize
where
    P: FnMut(&K, &V) -> bool

Returns the index of the partition point of a sorted map according to the given predicate (the index of the first element of the second partition).

See slice::partition_point for more details.

Computes in O(log(n)) time.

fn reverse(self: &mut Self)

Reverses the order of the map’s key-value pairs in place.

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

fn as_slice(self: &Self) -> &Slice<K, V>

Returns a slice of all the key-value pairs in the map.

Computes in O(1) time.

fn as_mut_slice(self: &mut Self) -> &mut Slice<K, V>

Returns a mutable slice of all the key-value pairs in the map.

Computes in O(1) time.

fn into_boxed_slice(self: Self) -> Box<Slice<K, V>>

Converts into a boxed slice of all the key-value pairs in the map.

Note that this will drop the inner hash table and any excess capacity.

fn get_index(self: &Self, index: usize) -> Option<(&K, &V)>

Get a key-value pair by index

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

Computes in O(1) time.

fn get_index_mut(self: &mut Self, index: usize) -> Option<(&K, &mut V)>

Get a key-value pair by index

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

Computes in O(1) time.

fn get_index_entry(self: &mut Self, index: usize) -> Option<IndexedEntry<'_, K, V>>

Get an entry in the map by index for in-place manipulation.

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

Computes in O(1) time.

fn get_disjoint_indices_mut<N: usize>(self: &mut Self, indices: [usize; N]) -> Result<[(&K, &mut V); N], GetDisjointMutError>

Get an array of N key-value pairs by N indices

Valid indices are 0 <= index < self.len() and each index needs to be unique.

Examples

let mut map = indexmap::IndexMap::from([(1, 'a'), (3, 'b'), (2, 'c')]);
assert_eq!(map.get_disjoint_indices_mut([2, 0]), Ok([(&2, &mut 'c'), (&1, &mut 'a')]));

fn get_range<R: RangeBounds<usize>>(self: &Self, range: R) -> Option<&Slice<K, V>>

Returns a slice of key-value pairs in the given range of indices.

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

Computes in O(1) time.

fn get_range_mut<R: RangeBounds<usize>>(self: &mut Self, range: R) -> Option<&mut Slice<K, V>>

Returns a mutable slice of key-value pairs in the given range of indices.

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

Computes in O(1) time.

fn first(self: &Self) -> Option<(&K, &V)>

Get the first key-value pair

Computes in O(1) time.

fn first_mut(self: &mut Self) -> Option<(&K, &mut V)>

Get the first key-value pair, with mutable access to the value

Computes in O(1) time.

fn first_entry(self: &mut Self) -> Option<IndexedEntry<'_, K, V>>

Get the first entry in the map for in-place manipulation.

Computes in O(1) time.

fn last(self: &Self) -> Option<(&K, &V)>

Get the last key-value pair

Computes in O(1) time.

fn last_mut(self: &mut Self) -> Option<(&K, &mut V)>

Get the last key-value pair, with mutable access to the value

Computes in O(1) time.

fn last_entry(self: &mut Self) -> Option<IndexedEntry<'_, K, V>>

Get the last entry in the map for in-place manipulation.

Computes in O(1) time.

fn swap_remove_index(self: &mut Self, index: usize) -> Option<(K, V)>

Remove the key-value pair by index

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

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

Computes in O(1) time (average).

fn shift_remove_index(self: &mut Self, index: usize) -> Option<(K, V)>

Remove the key-value pair by index

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

Like Vec::remove, the pair 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).

fn move_index(self: &mut Self, from: usize, to: usize)

Moves the position of a key-value pair from one index to another by shifting all other pairs in-between.

  • If from < to, the other pairs will shift down while the targeted pair moves up.
  • If from > to, the other pairs will shift up while the targeted pair moves down.

Panics if from or to are out of bounds.

Computes in O(n) time (average).

fn swap_indices(self: &mut Self, a: usize, b: usize)

Swaps the position of two key-value pairs in the map.

Panics if a or b are out of bounds.

Computes in O(1) time (average).

impl<K, V, S> IndexMap<K, V, S>

fn contains_key<Q>(self: &Self, key: &Q) -> bool
where
    Q: ?Sized + Hash + Equivalent<K>

Return true if an equivalent to key exists in the map.

Computes in O(1) time (average).

fn get<Q>(self: &Self, key: &Q) -> Option<&V>
where
    Q: ?Sized + Hash + Equivalent<K>

Return a reference to the value stored for key, if it is present, else None.

Computes in O(1) time (average).

fn get_key_value<Q>(self: &Self, key: &Q) -> Option<(&K, &V)>
where
    Q: ?Sized + Hash + Equivalent<K>

Return references to the key-value pair stored for key, if it is present, else None.

Computes in O(1) time (average).

fn get_full<Q>(self: &Self, key: &Q) -> Option<(usize, &K, &V)>
where
    Q: ?Sized + Hash + Equivalent<K>

Return item index, key and value

fn get_index_of<Q>(self: &Self, key: &Q) -> Option<usize>
where
    Q: ?Sized + Hash + Equivalent<K>

Return item index, if it exists in the map

Computes in O(1) time (average).

fn get_mut<Q>(self: &mut Self, key: &Q) -> Option<&mut V>
where
    Q: ?Sized + Hash + Equivalent<K>
fn get_full_mut<Q>(self: &mut Self, key: &Q) -> Option<(usize, &K, &mut V)>
where
    Q: ?Sized + Hash + Equivalent<K>
fn get_disjoint_mut<Q, N: usize>(self: &mut Self, keys: [&Q; N]) -> [Option<&mut V>; N]
where
    Q: ?Sized + Hash + Equivalent<K>

Return the values for N keys. If any key is duplicated, this function will panic.

Examples

let mut map = indexmap::IndexMap::from([(1, 'a'), (3, 'b'), (2, 'c')]);
assert_eq!(map.get_disjoint_mut([&2, &1]), [Some(&mut 'c'), Some(&mut 'a')]);

fn remove<Q>(self: &mut Self, key: &Q) -> Option<V>
where
    Q: ?Sized + Hash + Equivalent<K>

Remove the key-value pair equivalent to key and return its value.

NOTE: This is equivalent to [.swap_remove(key)][Self::swap_remove], replacing this entry's position with the last element, and it is deprecated in favor of calling that explicitly. If you need to preserve the relative order of the keys in the map, use [.shift_remove(key)][Self::shift_remove] instead.

fn remove_entry<Q>(self: &mut Self, key: &Q) -> Option<(K, V)>
where
    Q: ?Sized + Hash + Equivalent<K>

Remove and return the key-value pair equivalent to key.

NOTE: This is equivalent to [.swap_remove_entry(key)][Self::swap_remove_entry], replacing this entry's position with the last element, and it is deprecated in favor of calling that explicitly. If you need to preserve the relative order of the keys in the map, use [.shift_remove_entry(key)][Self::shift_remove_entry] instead.

fn swap_remove<Q>(self: &mut Self, key: &Q) -> Option<V>
where
    Q: ?Sized + Hash + Equivalent<K>

Remove the key-value pair equivalent to key and return its value.

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

Return None if key is not in map.

Computes in O(1) time (average).

fn swap_remove_entry<Q>(self: &mut Self, key: &Q) -> Option<(K, V)>
where
    Q: ?Sized + Hash + Equivalent<K>

Remove and return the key-value pair equivalent to key.

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

Return None if key is not in map.

Computes in O(1) time (average).

fn swap_remove_full<Q>(self: &mut Self, key: &Q) -> Option<(usize, K, V)>
where
    Q: ?Sized + Hash + Equivalent<K>

Remove the key-value pair equivalent to key and return it and the index it had.

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

Return None if key is not in map.

Computes in O(1) time (average).

fn shift_remove<Q>(self: &mut Self, key: &Q) -> Option<V>
where
    Q: ?Sized + Hash + Equivalent<K>

Remove the key-value pair equivalent to key and return its value.

Like Vec::remove, the pair 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 key is not in map.

Computes in O(n) time (average).

fn shift_remove_entry<Q>(self: &mut Self, key: &Q) -> Option<(K, V)>
where
    Q: ?Sized + Hash + Equivalent<K>

Remove and return the key-value pair equivalent to key.

Like Vec::remove, the pair 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 key is not in map.

Computes in O(n) time (average).

fn shift_remove_full<Q>(self: &mut Self, key: &Q) -> Option<(usize, K, V)>
where
    Q: ?Sized + Hash + Equivalent<K>

Remove the key-value pair equivalent to key and return it and the index it had.

Like Vec::remove, the pair 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 key is not in map.

Computes in O(n) time (average).

impl<K, V, S> IndexMap<K, V, S>

fn with_capacity_and_hasher(n: usize, hash_builder: S) -> Self

Create a new map with capacity for n key-value pairs. (Does not allocate if n is zero.)

Computes in O(n) time.

const fn with_hasher(hash_builder: S) -> Self

Create a new map with hash_builder.

This function is const, so it can be called in static contexts.

fn capacity(self: &Self) -> usize

Return the number of elements the map can hold without reallocating.

This number is a lower bound; the map might be able to hold more, but is guaranteed to be able to hold at least this many.

Computes in O(1) time.

fn hasher(self: &Self) -> &S

Return a reference to the map's BuildHasher.

fn len(self: &Self) -> usize

Return the number of key-value pairs in the map.

Computes in O(1) time.

fn is_empty(self: &Self) -> bool

Returns true if the map contains no elements.

Computes in O(1) time.

fn iter(self: &Self) -> Iter<'_, K, V>

Return an iterator over the key-value pairs of the map, in their order

fn iter_mut(self: &mut Self) -> IterMut<'_, K, V>

Return an iterator over the key-value pairs of the map, in their order

fn keys(self: &Self) -> Keys<'_, K, V>

Return an iterator over the keys of the map, in their order

fn into_keys(self: Self) -> IntoKeys<K, V>

Return an owning iterator over the keys of the map, in their order

fn values(self: &Self) -> Values<'_, K, V>

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

fn values_mut(self: &mut Self) -> ValuesMut<'_, K, V>

Return an iterator over mutable references to the values of the map, in their order

fn into_values(self: Self) -> IntoValues<K, V>

Return an owning iterator over the values of the map, in their order

fn clear(self: &mut Self)

Remove all key-value pairs in the map, while preserving its capacity.

Computes in O(n) time.

fn truncate(self: &mut Self, len: usize)

Shortens the map, keeping the first len elements and dropping the rest.

If len is greater than the map's current length, this has no effect.

fn drain<R>(self: &mut Self, range: R) -> Drain<'_, K, V>
where
    R: RangeBounds<usize>

Clears the IndexMap in the given index range, returning those key-value pairs 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 map entirely, use RangeFull like map.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 map.

fn extract_if<F, R>(self: &mut Self, range: R, pred: F) -> ExtractIf<'_, K, V, F>
where
    F: FnMut(&K, &mut V) -> bool,
    R: RangeBounds<usize>

Creates an iterator which uses a closure to determine if an element should be removed, for all elements in the given range.

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

Note that extract_if lets you mutate every value in the filter closure, regardless of whether you choose to keep or remove it.

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 check the entire map, use RangeFull like map.extract_if(.., predicate).

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 retain with a negated predicate if you do not need the returned iterator.

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

Examples

Splitting a map into even and odd keys, reusing the original map:

use indexmap::IndexMap;

let mut map: IndexMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
let extracted: IndexMap<i32, i32> = map.extract_if(.., |k, _v| k % 2 == 0).collect();

let evens = extracted.keys().copied().collect::<Vec<_>>();
let odds = map.keys().copied().collect::<Vec<_>>();

assert_eq!(evens, vec![0, 2, 4, 6]);
assert_eq!(odds, vec![1, 3, 5, 7]);

fn split_off(self: &mut Self, at: usize) -> Self
where
    S: Clone

Splits the collection into two at the given index.

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

Panics if at > len.

fn reserve(self: &mut Self, additional: usize)

Reserve capacity for additional more key-value pairs.

Computes in O(n) time.

fn reserve_exact(self: &mut Self, additional: usize)

Reserve capacity for additional more key-value pairs, without over-allocating.

Unlike reserve, this does not deliberately over-allocate the entry capacity to avoid frequent re-allocations. However, the underlying data structures may still have internal capacity requirements, and the allocator itself may give more space than requested, so this cannot be relied upon to be precisely minimal.

Computes in O(n) time.

fn try_reserve(self: &mut Self, additional: usize) -> Result<(), TryReserveError>

Try to reserve capacity for additional more key-value pairs.

Computes in O(n) time.

fn try_reserve_exact(self: &mut Self, additional: usize) -> Result<(), TryReserveError>

Try to reserve capacity for additional more key-value pairs, without over-allocating.

Unlike try_reserve, this does not deliberately over-allocate the entry capacity to avoid frequent re-allocations. However, the underlying data structures may still have internal capacity requirements, and the allocator itself may give more space than requested, so this cannot be relied upon to be precisely minimal.

Computes in O(n) time.

fn shrink_to_fit(self: &mut Self)

Shrink the capacity of the map as much as possible.

Computes in O(n) time.

fn shrink_to(self: &mut Self, min_capacity: usize)

Shrink the capacity of the map with a lower limit.

Computes in O(n) time.

impl<'a, K, V, S> Extend for IndexMap<K, V, S>

fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(self: &mut Self, iterable: I)

Extend the map with all key-value pairs in the iterable.

See the first extend method for more details.

impl<K, V, N: usize> From for IndexMap<K, V, std::collections::hash_map::RandomState>

fn from(arr: [(K, V); N]) -> Self

Examples

use indexmap::IndexMap;

let map1 = IndexMap::from([(1, 2), (3, 4)]);
let map2: IndexMap<_, _> = [(1, 2), (3, 4)].into();
assert_eq!(map1, map2);

impl<K, V, Q, S> Index for IndexMap<K, V, S>

fn index(self: &Self, key: &Q) -> &V

Returns a reference to the value corresponding to the supplied key.

Panics if key is not present in the map.

impl<K, V, Q, S> IndexMut for IndexMap<K, V, S>

fn index_mut(self: &mut Self, key: &Q) -> &mut V

Returns a mutable reference to the value corresponding to the supplied key.

Panics if key is not present in the map.

impl<K, V, S> Clone for IndexMap<K, V, S>

fn clone(self: &Self) -> Self
fn clone_from(self: &mut Self, other: &Self)

impl<K, V, S> Debug for IndexMap<K, V, S>

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

impl<K, V, S> Default for IndexMap<K, V, S>

fn default() -> Self

Return an empty IndexMap

impl<K, V, S> Eq for IndexMap<K, V, S>

impl<K, V, S> Extend for IndexMap<K, V, S>

fn extend<I: IntoIterator<Item = (K, V)>>(self: &mut Self, iterable: I)

Extend the map with all key-value pairs in the iterable.

This is equivalent to calling [insert][IndexMap::insert] for each of them in order, which means that for keys that already existed in the map, their value is updated but it keeps the existing order.

New keys are inserted in the order they appear in the sequence. If equivalents of a key occur more than once, the last corresponding value prevails.

impl<K, V, S> Freeze for IndexMap<K, V, S>

impl<K, V, S> FromIterator for IndexMap<K, V, S>

fn from_iter<I: IntoIterator<Item = (K, V)>>(iterable: I) -> Self

Create an IndexMap from the sequence of key-value pairs in the iterable.

from_iter uses the same logic as extend. See [extend][IndexMap::extend] for more details.

impl<K, V, S> Index for IndexMap<K, V, S>

fn index(self: &Self, range: ops::Range<usize>) -> &<Self as >::Output

impl<K, V, S> Index for IndexMap<K, V, S>

fn index(self: &Self, range: ops::RangeFrom<usize>) -> &<Self as >::Output

impl<K, V, S> Index for IndexMap<K, V, S>

fn index(self: &Self, range: ops::RangeFull) -> &<Self as >::Output

impl<K, V, S> Index for IndexMap<K, V, S>

fn index(self: &Self, range: ops::RangeInclusive<usize>) -> &<Self as >::Output

impl<K, V, S> Index for IndexMap<K, V, S>

fn index(self: &Self, range: ops::RangeTo<usize>) -> &<Self as >::Output

impl<K, V, S> Index for IndexMap<K, V, S>

fn index(self: &Self, range: ops::RangeToInclusive<usize>) -> &<Self as >::Output

impl<K, V, S> Index for IndexMap<K, V, S>

fn index(self: &Self, range: (Bound<usize>, Bound<usize>)) -> &<Self as >::Output

impl<K, V, S> Index for IndexMap<K, V, S>

fn index(self: &Self, index: usize) -> &V

Returns a reference to the value at the supplied index.

Panics if index is out of bounds.

impl<K, V, S> IndexMut for IndexMap<K, V, S>

fn index_mut(self: &mut Self, range: ops::RangeFrom<usize>) -> &mut <Self as >::Output

impl<K, V, S> IndexMut for IndexMap<K, V, S>

fn index_mut(self: &mut Self, range: ops::RangeFull) -> &mut <Self as >::Output

impl<K, V, S> IndexMut for IndexMap<K, V, S>

fn index_mut(self: &mut Self, range: ops::RangeInclusive<usize>) -> &mut <Self as >::Output

impl<K, V, S> IndexMut for IndexMap<K, V, S>

fn index_mut(self: &mut Self, range: ops::RangeTo<usize>) -> &mut <Self as >::Output

impl<K, V, S> IndexMut for IndexMap<K, V, S>

fn index_mut(self: &mut Self, range: ops::RangeToInclusive<usize>) -> &mut <Self as >::Output

impl<K, V, S> IndexMut for IndexMap<K, V, S>

fn index_mut(self: &mut Self, range: (Bound<usize>, Bound<usize>)) -> &mut <Self as >::Output

impl<K, V, S> IndexMut for IndexMap<K, V, S>

fn index_mut(self: &mut Self, index: usize) -> &mut V

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

Panics if index is out of bounds.

impl<K, V, S> IndexMut for IndexMap<K, V, S>

fn index_mut(self: &mut Self, range: ops::Range<usize>) -> &mut <Self as >::Output

impl<K, V, S> IntoIterator for super::IndexMap<K, V, S>

fn into_iter(self: Self) -> <Self as >::IntoIter

impl<K, V, S> MutableKeys for super::IndexMap<K, V, S>

fn get_full_mut2<Q>(self: &mut Self, key: &Q) -> Option<(usize, &mut K, &mut V)>
where
    Q: ?Sized + Hash + Equivalent<K>
fn get_index_mut2(self: &mut Self, index: usize) -> Option<(&mut K, &mut V)>
fn iter_mut2(self: &mut Self) -> IterMut2<'_, <Self as >::Key, <Self as >::Value>
fn retain2<F>(self: &mut Self, keep: F)
where
    F: FnMut(&mut K, &mut V) -> bool

impl<K, V, S> RawEntryApiV1 for crate::IndexMap<K, V, S>

fn raw_entry_v1(self: &Self) -> RawEntryBuilder<'_, K, V, S>
fn raw_entry_mut_v1(self: &mut Self) -> RawEntryBuilderMut<'_, K, V, S>

impl<K, V, S> RefUnwindSafe for IndexMap<K, V, S>

impl<K, V, S> Send for IndexMap<K, V, S>

impl<K, V, S> Sync for IndexMap<K, V, S>

impl<K, V, S> Unpin for IndexMap<K, V, S>

impl<K, V, S> UnwindSafe for IndexMap<K, V, S>

impl<K, V1, S1, V2, S2> PartialEq for IndexMap<K, V1, S1>

fn eq(self: &Self, other: &IndexMap<K, V2, S2>) -> bool

impl<Q, K> Equivalent for IndexMap<K, V, S>

fn equivalent(self: &Self, key: &K) -> bool

impl<Q, K> Equivalent for IndexMap<K, V, S>

fn equivalent(self: &Self, key: &K) -> bool

impl<T> Any for IndexMap<K, V, S>

fn type_id(self: &Self) -> TypeId

impl<T> Borrow for IndexMap<K, V, S>

fn borrow(self: &Self) -> &T

impl<T> BorrowMut for IndexMap<K, V, S>

fn borrow_mut(self: &mut Self) -> &mut T

impl<T> CloneToUninit for IndexMap<K, V, S>

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

impl<T> From for IndexMap<K, V, S>

fn from(t: T) -> T

Returns the argument unchanged.

impl<T> ToOwned for IndexMap<K, V, S>

fn to_owned(self: &Self) -> T
fn clone_into(self: &Self, target: &mut T)

impl<T, U> Into for IndexMap<K, V, S>

fn into(self: Self) -> U

Calls U::from(self).

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

impl<T, U> TryFrom for IndexMap<K, V, S>

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

impl<T, U> TryInto for IndexMap<K, V, S>

fn try_into(self: Self) -> Result<U, <U as TryFrom<T>>::Error>