Struct ordermap::OrderMap

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

A hash map with consistent order of the key-value pairs.

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.

Mutable Keys

Some methods expose &mut K, mutable references to the key as it is stored in the map. The key is allowed to be modified, but only in a way that preserves its hash and equality (it is only useful for composite key structs).

This is sound (memory safe) but a logical error hazard (just like implementing PartialEq, Eq, or Hash incorrectly would be).

Examples

use ordermap::OrderMap;

// count the frequency of each letter in a sentence.
let mut letters = OrderMap::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> OrderMap<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> OrderMap<K, V, S>

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

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

Computes in O(n) time.

fn len(&self) -> usize

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

Computes in O(1) time.

fn capacity(&self) -> usize

Computes in O(1) time.

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

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

Get the given key’s corresponding entry in the map for in-place manipulation.

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

fn clear(&mut self)

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

Computes in O(n) time.

fn reserve(&mut self, additional: usize)

FIXME Not implemented fully yet

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

Insert they key-value pair into the map.

If a value already existed for key, that old value is returned in Some; otherwise, return None.

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

fn iter(&self) -> Iter<K, V>

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

fn iter_mut(&mut self) -> IterMut<K, V>

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

fn keys(&self) -> Keys<K, V>

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

fn values(&self) -> Values<K, V>

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

fn values_mut(&mut self) -> ValuesMut<K, V>

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

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

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

Computes in O(1) time (average).

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

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

Computes in O(1) time (average).

fn get_pair<Q: ?Sized>(&self, key: &Q) -> Option<(&K, &V)> where K: Borrow<Q>, Q: Eq + Hash

fn get_pair_index<Q: ?Sized>(&self, key: &Q) -> Option<(usize, &K, &V)> where K: Borrow<Q>, Q: Eq + Hash

Return item index, key and value

fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V> where K: Borrow<Q>, Q: Eq + Hash

fn get_pair_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<(&mut K, &mut V)> where K: Borrow<Q>, Q: Eq + Hash

fn get_pair_index_mut<Q: ?Sized>(&mut self,
                                 key: &Q)
                                 -> Option<(usize, &mut K, &mut V)> where K: Borrow<Q>, Q: Eq + Hash

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

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).

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

FIXME Same as .swap_remove

Computes in O(1) time (average).

fn swap_remove_pair<Q: ?Sized>(&mut self, key: &Q) -> Option<(K, V)> where K: Borrow<Q>, Q: Eq + Hash

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

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.

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

Remove the last key-value pair

Computes in O(1) time (average).

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

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

The order the elements are visited is not specified.

Computes in O(n) time (average).

impl<K, V, S> OrderMap<K, V, S>

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

Get a key-value pair by index

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

Computes in O(1) time.

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

Remove the key-value pair by index

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

Computes in O(1) time (average).

Trait Implementations

impl<K: Clone, V: Clone, S: Clone> Clone for OrderMap<K, V, S>

fn clone(&self) -> OrderMap<K, V, S>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

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

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

Formats the value using the given formatter.

impl<'a, K, V, S> IntoIterator for &'a OrderMap<K, V, S> where K: Hash + Eq,
        S: BuildHasher

type Item = (&'a K, &'a V)

The type of the elements being iterated over.

type IntoIter = Iter<'a, K, V>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a, K, V, S> IntoIterator for &'a mut OrderMap<K, V, S> where K: Hash + Eq,
        S: BuildHasher

type Item = (&'a K, &'a mut V)

The type of the elements being iterated over.

type IntoIter = IterMut<'a, K, V>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

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

type Item = (K, V)

The type of the elements being iterated over.

type IntoIter = IntoIter<K, V>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a, K, V, Q: ?Sized, S> Index<&'a Q> for OrderMap<K, V, S> where K: Eq + Hash,
        K: Borrow<Q>,
        Q: Eq + Hash,
        S: BuildHasher

type Output = V

The returned type after indexing

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

Panics if key is not present in the map.

impl<'a, K, V, Q: ?Sized, S> IndexMut<&'a Q> for OrderMap<K, V, S> where K: Eq + Hash,
        K: Borrow<Q>,
        Q: Eq + Hash,
        S: BuildHasher

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().

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

Panics if key is not present in the map.

impl<K, V, S> FromIterator<(K, V)> for OrderMap<K, V, S> where K: Hash + Eq,
        S: BuildHasher + Default

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

Creates a value from an iterator.

impl<K, V, S> Extend<(K, V)> for OrderMap<K, V, S> where K: Hash + Eq,
        S: BuildHasher

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

Extends a collection with the contents of an iterator.

impl<K, V, S> Default for OrderMap<K, V, S> where S: BuildHasher + Default

fn default() -> Self

Returns the "default value" for a type.