Struct indexmap::map::IndexMap [] [src]

pub struct IndexMap<K, V, S = RandomState> { /* fields omitted */ }

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, 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() or .swap_remove() methods. Methods such as .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);

Methods

impl<K, V> IndexMap<K, V>
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Create a new map. (Does not allocate.)

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

Computes in O(n) time.

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

Computes in O(1) time.

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Returns true if the map contains no elements.

Computes in O(1) time.

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Create a new map with hash_builder

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Return a reference to the map's BuildHasher.

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Computes in O(1) time.

impl<K, V, S> IndexMap<K, V, S> where
    K: Hash + Eq,
    S: BuildHasher
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Remove all key-value pairs in the map, while preserving its capacity.

Computes in O(n) time.

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Reserve capacity for additional more key-value pairs.

FIXME Not implemented fully yet.

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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 if you you want to insert or modify or if you need to get the index of the corresponding key-value pair.

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

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

Important traits for Iter<'a, K, V>
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Return an iterator over the key-value pairs of the map, in their order

Important traits for IterMut<'a, K, V>
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Return an iterator over the key-value pairs of the map, in their order

Important traits for Keys<'a, K, V>
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Return an iterator over the keys of the map, in their order

Important traits for Values<'a, K, V>
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Return an iterator over the values of the map, in their order

Important traits for ValuesMut<'a, K, V>
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Return an iterator over mutable references to the the values of the map, in their order

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

Computes in O(1) time (average).

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

Computes in O(1) time (average).

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Return item index, key and value

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NOTE: Same as .swap_remove

Computes in O(1) time (average).

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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 postion of what used to be the last element!

Return None if key is not in map.

Computes in O(1) time (average).

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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 postion of what used to be the last element!

Return None if key is not in map.

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Remove the last key-value pair

Computes in O(1) time (average).

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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).

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

See sort_by for details.

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

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.

Important traits for IntoIter<K, V>
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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.

Important traits for Drain<'a, K, V>
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Clears the IndexMap, returning all key-value pairs as a drain iterator. Keeps the allocated memory for reuse.

impl<K, V, S> IndexMap<K, V, S>
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Get a key-value pair by index

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

Computes in O(1) time.

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Get a key-value pair by index

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

Computes in O(1) time.

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Remove the key-value pair by index

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

Computes in O(1) time (average).

Trait Implementations

impl<K, V, S> MutableKeys for IndexMap<K, V, S> where
    K: Eq + Hash,
    S: BuildHasher
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Opt-in mutable access to keys.

See MutableKeys for more information.

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Return item index, mutable reference to key and value

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Scan through each key-value pair in the map and keep those where the closure keep returns true. Read more

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This method is not useful in itself – it is there to “seal” the trait for external implementation, so that we can add methods without causing breaking changes. Read more

impl<K: Clone, V: Clone, S: Clone> Clone for IndexMap<K, V, S>
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Returns a copy of the value. Read more

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Performs copy-assignment from source. Read more

impl<K, V, S> Debug for IndexMap<K, V, S> where
    K: Debug + Hash + Eq,
    V: Debug,
    S: BuildHasher
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Formats the value using the given formatter. Read more

impl<'a, K, V, S> IntoIterator for &'a IndexMap<K, V, S> where
    K: Hash + Eq,
    S: BuildHasher
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The type of the elements being iterated over.

Which kind of iterator are we turning this into?

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Creates an iterator from a value. Read more

impl<'a, K, V, S> IntoIterator for &'a mut IndexMap<K, V, S> where
    K: Hash + Eq,
    S: BuildHasher
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The type of the elements being iterated over.

Which kind of iterator are we turning this into?

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Creates an iterator from a value. Read more

impl<K, V, S> IntoIterator for IndexMap<K, V, S> where
    K: Hash + Eq,
    S: BuildHasher
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The type of the elements being iterated over.

Which kind of iterator are we turning this into?

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Creates an iterator from a value. Read more

impl<'a, K, V, Q: ?Sized, S> Index<&'a Q> for IndexMap<K, V, S> where
    Q: Hash + Equivalent<K>,
    K: Hash + Eq,
    S: BuildHasher
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The returned type after indexing.

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Panics if key is not present in the map.

impl<'a, K, V, Q: ?Sized, S> IndexMut<&'a Q> for IndexMap<K, V, S> where
    Q: Hash + Equivalent<K>,
    K: Hash + Eq,
    S: BuildHasher
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Mutable indexing allows changing / updating values of key-value pairs that are already present.

You can not insert new pairs with index syntax, use .insert().

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Panics if key is not present in the map.

impl<K, V, S> FromIterator<(K, V)> for IndexMap<K, V, S> where
    K: Hash + Eq,
    S: BuildHasher + Default
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Create an IndexMap from the sequence of key-value pairs in the iterable.

from_iter uses the same logic as extend. See extend for more details.

impl<K, V, S> Extend<(K, V)> for IndexMap<K, V, S> where
    K: Hash + Eq,
    S: BuildHasher
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Extend the map with all key-value pairs in the iterable.

This is equivalent to calling 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 inserted in the order in the sequence. If equivalents of a key occur more than once, the last corresponding value prevails.

impl<'a, K, V, S> Extend<(&'a K, &'a V)> for IndexMap<K, V, S> where
    K: Hash + Eq + Copy,
    V: Copy,
    S: BuildHasher
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Extend the map with all key-value pairs in the iterable.

See the first extend method for more details.

impl<K, V, S> Default for IndexMap<K, V, S> where
    S: BuildHasher + Default
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Return an empty IndexMap

impl<K, V1, S1, V2, S2> PartialEq<IndexMap<K, V2, S2>> for IndexMap<K, V1, S1> where
    K: Hash + Eq,
    V1: PartialEq<V2>,
    S1: BuildHasher,
    S2: BuildHasher
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This method tests for self and other values to be equal, and is used by ==. Read more

1.0.0
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This method tests for !=.

impl<K, V, S> Eq for IndexMap<K, V, S> where
    K: Eq + Hash,
    V: Eq,
    S: BuildHasher
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