Expand description
An ordered map based on a B-Tree.
B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of comparisons necessary to find an element (log2n). However, in practice the way this is done is very inefficient for modern computer architectures. In particular, every element is stored in its own individually heap-allocated node. This means that every single insertion triggers a heap-allocation, and every single comparison should be a cache-miss. Since these are both notably expensive things to do in practice, we are forced to at very least reconsider the BST strategy.
A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing this, we reduce the number of allocations by a factor of B, and improve cache efficiency in searches. However, this does mean that searches will have to do more comparisons on average. The precise number of comparisons depends on the node search strategy used. For optimal cache efficiency, one could search the nodes linearly. For optimal comparisons, one could search the node using binary search. As a compromise, one could also perform a linear search that initially only checks every ith element for some choice of i.
Currently, our implementation simply performs naive linear search. This provides excellent performance on small nodes of elements which are cheap to compare. However in the future we would like to further explore choosing the optimal search strategy based on the choice of B, and possibly other factors. Using linear search, searching for a random element is expected to take B * log(n) comparisons, which is generally worse than a BST. In practice, however, performance is excellent.
It is a logic error for a key to be modified in such a way that the key’s ordering relative to
any other key, as determined by the Ord
trait, changes while it is in the map. This is
normally only possible through Cell
, RefCell
, global state, I/O, or unsafe code.
The behavior resulting from such a logic error is not specified, but will be encapsulated to the
BTreeMap
that observed the logic error and not result in undefined behavior. This could
include panics, incorrect results, aborts, memory leaks, and non-termination.
Iterators obtained from functions such as BTreeMap::iter
, BTreeMap::values
, or
BTreeMap::keys
produce their items in order by key, and take worst-case logarithmic and
amortized constant time per item returned.
Examples
use std::collections::BTreeMap;
// type inference lets us omit an explicit type signature (which
// would be `BTreeMap<&str, &str>` in this example).
let mut movie_reviews = BTreeMap::new();
// review some movies.
movie_reviews.insert("Office Space", "Deals with real issues in the workplace.");
movie_reviews.insert("Pulp Fiction", "Masterpiece.");
movie_reviews.insert("The Godfather", "Very enjoyable.");
movie_reviews.insert("The Blues Brothers", "Eye lyked it a lot.");
// check for a specific one.
if !movie_reviews.contains_key("Les Misérables") {
println!("We've got {} reviews, but Les Misérables ain't one.",
movie_reviews.len());
}
// oops, this review has a lot of spelling mistakes, let's delete it.
movie_reviews.remove("The Blues Brothers");
// look up the values associated with some keys.
let to_find = ["Up!", "Office Space"];
for movie in &to_find {
match movie_reviews.get(movie) {
Some(review) => println!("{movie}: {review}"),
None => println!("{movie} is unreviewed.")
}
}
// Look up the value for a key (will panic if the key is not found).
println!("Movie review: {}", movie_reviews["Office Space"]);
// iterate over everything.
for (movie, review) in &movie_reviews {
println!("{movie}: \"{review}\"");
}
RunA BTreeMap
with a known list of items can be initialized from an array:
use std::collections::BTreeMap;
let solar_distance = BTreeMap::from([
("Mercury", 0.4),
("Venus", 0.7),
("Earth", 1.0),
("Mars", 1.5),
]);
RunBTreeMap
implements an Entry API
, which allows for complex
methods of getting, setting, updating and removing keys and their values:
use std::collections::BTreeMap;
// type inference lets us omit an explicit type signature (which
// would be `BTreeMap<&str, u8>` in this example).
let mut player_stats = BTreeMap::new();
fn random_stat_buff() -> u8 {
// could actually return some random value here - let's just return
// some fixed value for now
42
}
// insert a key only if it doesn't already exist
player_stats.entry("health").or_insert(100);
// insert a key using a function that provides a new value only if it
// doesn't already exist
player_stats.entry("defence").or_insert_with(random_stat_buff);
// update a key, guarding against the key possibly not being set
let stat = player_stats.entry("attack").or_insert(100);
*stat += random_stat_buff();
// modify an entry before an insert with in-place mutation
player_stats.entry("mana").and_modify(|mana| *mana += 200).or_insert(100);
RunImplementations
sourceimpl<K, V, A> BTreeMap<K, V, A>where
A: Allocator + Clone,
impl<K, V, A> BTreeMap<K, V, A>where
A: Allocator + Clone,
sourceimpl<K, V, A> BTreeMap<K, V, A>where
A: Allocator + Clone,
impl<K, V, A> BTreeMap<K, V, A>where
A: Allocator + Clone,
sourcepub fn get<Q>(&self, key: &Q) -> Option<&V>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
pub fn get<Q>(&self, key: &Q) -> Option<&V>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
Returns a reference to the value corresponding to the key.
The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.get(&1), Some(&"a"));
assert_eq!(map.get(&2), None);
Run1.40.0 · sourcepub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
Returns the key-value pair corresponding to the supplied key.
The supplied key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.
Examples
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
assert_eq!(map.get_key_value(&2), None);
Run1.66.0-dev · sourcepub fn first_key_value(&self) -> Option<(&K, &V)>where
K: Ord,
pub fn first_key_value(&self) -> Option<(&K, &V)>where
K: Ord,
Returns the first key-value pair in the map. The key in this pair is the minimum key in the map.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
assert_eq!(map.first_key_value(), None);
map.insert(1, "b");
map.insert(2, "a");
assert_eq!(map.first_key_value(), Some((&1, &"b")));
Run1.66.0-dev · sourcepub fn first_entry(&mut self) -> Option<OccupiedEntry<'_, K, V, A>>where
K: Ord,
pub fn first_entry(&mut self) -> Option<OccupiedEntry<'_, K, V, A>>where
K: Ord,
Returns the first entry in the map for in-place manipulation. The key of this entry is the minimum key in the map.
Examples
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
map.insert(2, "b");
if let Some(mut entry) = map.first_entry() {
if *entry.key() > 0 {
entry.insert("first");
}
}
assert_eq!(*map.get(&1).unwrap(), "first");
assert_eq!(*map.get(&2).unwrap(), "b");
Run1.66.0-dev · sourcepub fn pop_first(&mut self) -> Option<(K, V)>where
K: Ord,
pub fn pop_first(&mut self) -> Option<(K, V)>where
K: Ord,
Removes and returns the first element in the map. The key of this element is the minimum key that was in the map.
Examples
Draining elements in ascending order, while keeping a usable map each iteration.
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
map.insert(2, "b");
while let Some((key, _val)) = map.pop_first() {
assert!(map.iter().all(|(k, _v)| *k > key));
}
assert!(map.is_empty());
Run1.66.0-dev · sourcepub fn last_entry(&mut self) -> Option<OccupiedEntry<'_, K, V, A>>where
K: Ord,
pub fn last_entry(&mut self) -> Option<OccupiedEntry<'_, K, V, A>>where
K: Ord,
Returns the last entry in the map for in-place manipulation. The key of this entry is the maximum key in the map.
Examples
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
map.insert(2, "b");
if let Some(mut entry) = map.last_entry() {
if *entry.key() > 0 {
entry.insert("last");
}
}
assert_eq!(*map.get(&1).unwrap(), "a");
assert_eq!(*map.get(&2).unwrap(), "last");
Run1.66.0-dev · sourcepub fn pop_last(&mut self) -> Option<(K, V)>where
K: Ord,
pub fn pop_last(&mut self) -> Option<(K, V)>where
K: Ord,
Removes and returns the last element in the map. The key of this element is the maximum key that was in the map.
Examples
Draining elements in descending order, while keeping a usable map each iteration.
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
map.insert(2, "b");
while let Some((key, _val)) = map.pop_last() {
assert!(map.iter().all(|(k, _v)| *k < key));
}
assert!(map.is_empty());
Runsourcepub fn contains_key<Q>(&self, key: &Q) -> boolwhere
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
pub fn contains_key<Q>(&self, key: &Q) -> boolwhere
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
Returns true
if the map contains a value for the specified key.
The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&2), false);
Runsourcepub fn get_mut<Q>(&mut self, key: &Q) -> Option<&mut V>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
pub fn get_mut<Q>(&mut self, key: &Q) -> Option<&mut V>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
Returns a mutable reference to the value corresponding to the key.
The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
if let Some(x) = map.get_mut(&1) {
*x = "b";
}
assert_eq!(map[&1], "b");
Runsourcepub fn insert(&mut self, key: K, value: V) -> Option<V>where
K: Ord,
pub fn insert(&mut self, key: K, value: V) -> Option<V>where
K: Ord,
Inserts a key-value pair into the map.
If the map did not have this key present, None
is returned.
If the map did have this key present, the value is updated, and the old
value is returned. The key is not updated, though; this matters for
types that can be ==
without being identical. See the module-level
documentation for more.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
assert_eq!(map.insert(37, "a"), None);
assert_eq!(map.is_empty(), false);
map.insert(37, "b");
assert_eq!(map.insert(37, "c"), Some("b"));
assert_eq!(map[&37], "c");
Runsourcepub fn try_insert(
&mut self,
key: K,
value: V
) -> Result<&mut V, OccupiedError<'_, K, V, A>>where
K: Ord,
🔬This is a nightly-only experimental API. (map_try_insert
#82766)
pub fn try_insert(
&mut self,
key: K,
value: V
) -> Result<&mut V, OccupiedError<'_, K, V, A>>where
K: Ord,
map_try_insert
#82766)Tries to insert a key-value pair into the map, and returns a mutable reference to the value in the entry.
If the map already had this key present, nothing is updated, and an error containing the occupied entry and the value is returned.
Examples
Basic usage:
#![feature(map_try_insert)]
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
assert_eq!(map.try_insert(37, "a").unwrap(), &"a");
let err = map.try_insert(37, "b").unwrap_err();
assert_eq!(err.entry.key(), &37);
assert_eq!(err.entry.get(), &"a");
assert_eq!(err.value, "b");
Runsourcepub fn remove<Q>(&mut self, key: &Q) -> Option<V>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
pub fn remove<Q>(&mut self, key: &Q) -> Option<V>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
Removes a key from the map, returning the value at the key if the key was previously in the map.
The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.remove(&1), Some("a"));
assert_eq!(map.remove(&1), None);
Run1.45.0 · sourcepub fn remove_entry<Q>(&mut self, key: &Q) -> Option<(K, V)>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
pub fn remove_entry<Q>(&mut self, key: &Q) -> Option<(K, V)>where
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
Removes a key from the map, returning the stored key and value if the key was previously in the map.
The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.remove_entry(&1), Some((1, "a")));
assert_eq!(map.remove_entry(&1), None);
Run1.53.0 · sourcepub fn retain<F>(&mut self, f: F)where
K: Ord,
F: FnMut(&K, &mut V) -> bool,
pub fn retain<F>(&mut self, f: F)where
K: Ord,
F: FnMut(&K, &mut V) -> bool,
Retains only the elements specified by the predicate.
In other words, remove all pairs (k, v)
for which f(&k, &mut v)
returns false
.
The elements are visited in ascending key order.
Examples
use std::collections::BTreeMap;
let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x*10)).collect();
// Keep only the elements with even-numbered keys.
map.retain(|&k, _| k % 2 == 0);
assert!(map.into_iter().eq(vec![(0, 0), (2, 20), (4, 40), (6, 60)]));
Run1.11.0 · sourcepub fn append(&mut self, other: &mut BTreeMap<K, V, A>)where
K: Ord,
A: Clone,
pub fn append(&mut self, other: &mut BTreeMap<K, V, A>)where
K: Ord,
A: Clone,
Moves all elements from other
into self
, leaving other
empty.
Examples
use std::collections::BTreeMap;
let mut a = BTreeMap::new();
a.insert(1, "a");
a.insert(2, "b");
a.insert(3, "c");
let mut b = BTreeMap::new();
b.insert(3, "d");
b.insert(4, "e");
b.insert(5, "f");
a.append(&mut b);
assert_eq!(a.len(), 5);
assert_eq!(b.len(), 0);
assert_eq!(a[&1], "a");
assert_eq!(a[&2], "b");
assert_eq!(a[&3], "d");
assert_eq!(a[&4], "e");
assert_eq!(a[&5], "f");
Run1.17.0 · sourcepub fn range<T, R>(&self, range: R) -> Range<'_, K, V>ⓘNotable traits for Range<'a, K, V>impl<'a, K, V> Iterator for Range<'a, K, V> type Item = (&'a K, &'a V);
where
T: Ord + ?Sized,
K: Borrow<T> + Ord,
R: RangeBounds<T>,
pub fn range<T, R>(&self, range: R) -> Range<'_, K, V>ⓘNotable traits for Range<'a, K, V>impl<'a, K, V> Iterator for Range<'a, K, V> type Item = (&'a K, &'a V);
where
T: Ord + ?Sized,
K: Borrow<T> + Ord,
R: RangeBounds<T>,
Constructs a double-ended iterator over a sub-range of elements in the map.
The simplest way is to use the range syntax min..max
, thus range(min..max)
will
yield elements from min (inclusive) to max (exclusive).
The range may also be entered as (Bound<T>, Bound<T>)
, so for example
range((Excluded(4), Included(10)))
will yield a left-exclusive, right-inclusive
range from 4 to 10.
Panics
Panics if range start > end
.
Panics if range start == end
and both bounds are Excluded
.
Examples
Basic usage:
use std::collections::BTreeMap;
use std::ops::Bound::Included;
let mut map = BTreeMap::new();
map.insert(3, "a");
map.insert(5, "b");
map.insert(8, "c");
for (&key, &value) in map.range((Included(&4), Included(&8))) {
println!("{key}: {value}");
}
assert_eq!(Some((&5, &"b")), map.range(4..).next());
Run1.17.0 · sourcepub fn range_mut<T, R>(&mut self, range: R) -> RangeMut<'_, K, V>ⓘNotable traits for RangeMut<'a, K, V>impl<'a, K, V> Iterator for RangeMut<'a, K, V> type Item = (&'a K, &'a mut V);
where
T: Ord + ?Sized,
K: Borrow<T> + Ord,
R: RangeBounds<T>,
pub fn range_mut<T, R>(&mut self, range: R) -> RangeMut<'_, K, V>ⓘNotable traits for RangeMut<'a, K, V>impl<'a, K, V> Iterator for RangeMut<'a, K, V> type Item = (&'a K, &'a mut V);
where
T: Ord + ?Sized,
K: Borrow<T> + Ord,
R: RangeBounds<T>,
Constructs a mutable double-ended iterator over a sub-range of elements in the map.
The simplest way is to use the range syntax min..max
, thus range(min..max)
will
yield elements from min (inclusive) to max (exclusive).
The range may also be entered as (Bound<T>, Bound<T>)
, so for example
range((Excluded(4), Included(10)))
will yield a left-exclusive, right-inclusive
range from 4 to 10.
Panics
Panics if range start > end
.
Panics if range start == end
and both bounds are Excluded
.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map: BTreeMap<&str, i32> =
[("Alice", 0), ("Bob", 0), ("Carol", 0), ("Cheryl", 0)].into();
for (_, balance) in map.range_mut("B".."Cheryl") {
*balance += 100;
}
for (name, balance) in &map {
println!("{name} => {balance}");
}
Runsourcepub fn entry(&mut self, key: K) -> Entry<'_, K, V, A>where
K: Ord,
pub fn entry(&mut self, key: K) -> Entry<'_, K, V, A>where
K: Ord,
Gets the given key’s corresponding entry in the map for in-place manipulation.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut count: BTreeMap<&str, usize> = BTreeMap::new();
// count the number of occurrences of letters in the vec
for x in ["a", "b", "a", "c", "a", "b"] {
count.entry(x).and_modify(|curr| *curr += 1).or_insert(1);
}
assert_eq!(count["a"], 3);
assert_eq!(count["b"], 2);
assert_eq!(count["c"], 1);
Run1.11.0 · sourcepub fn split_off<Q>(&mut self, key: &Q) -> BTreeMap<K, V, A>where
Q: Ord + ?Sized,
K: Borrow<Q> + Ord,
A: Clone,
pub fn split_off<Q>(&mut self, key: &Q) -> BTreeMap<K, V, A>where
Q: Ord + ?Sized,
K: Borrow<Q> + Ord,
A: Clone,
Splits the collection into two at the given key. Returns everything after the given key, including the key.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut a = BTreeMap::new();
a.insert(1, "a");
a.insert(2, "b");
a.insert(3, "c");
a.insert(17, "d");
a.insert(41, "e");
let b = a.split_off(&3);
assert_eq!(a.len(), 2);
assert_eq!(b.len(), 3);
assert_eq!(a[&1], "a");
assert_eq!(a[&2], "b");
assert_eq!(b[&3], "c");
assert_eq!(b[&17], "d");
assert_eq!(b[&41], "e");
Runsourcepub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F, A>ⓘNotable traits for DrainFilter<'_, K, V, F, A>impl<K, V, F, A> Iterator for DrainFilter<'_, K, V, F, A>where
A: Allocator + Clone,
F: FnMut(&K, &mut V) -> bool, type Item = (K, V);
where
K: Ord,
F: FnMut(&K, &mut V) -> bool,
🔬This is a nightly-only experimental API. (btree_drain_filter
#70530)
pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F, A>ⓘNotable traits for DrainFilter<'_, K, V, F, A>impl<K, V, F, A> Iterator for DrainFilter<'_, K, V, F, A>where
A: Allocator + Clone,
F: FnMut(&K, &mut V) -> bool, type Item = (K, V);
where
K: Ord,
F: FnMut(&K, &mut V) -> bool,
A: Allocator + Clone,
F: FnMut(&K, &mut V) -> bool, type Item = (K, V);
btree_drain_filter
#70530)Creates an iterator that visits all elements (key-value pairs) in
ascending key order and uses a closure to determine if an element should
be removed. 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.
The iterator also lets you mutate the value of each element in the closure, regardless of whether you choose to keep or remove it.
If the iterator is only partially consumed or not consumed at all, each
of the remaining elements is still subjected to the closure, which may
change its value and, by returning true
, have the element removed and
dropped.
It is unspecified how many more elements will be subjected to the
closure if a panic occurs in the closure, or a panic occurs while
dropping an element, or if the DrainFilter
value is leaked.
Examples
Splitting a map into even and odd keys, reusing the original map:
#![feature(btree_drain_filter)]
use std::collections::BTreeMap;
let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
let evens: BTreeMap<_, _> = map.drain_filter(|k, _v| k % 2 == 0).collect();
let odds = map;
assert_eq!(evens.keys().copied().collect::<Vec<_>>(), [0, 2, 4, 6]);
assert_eq!(odds.keys().copied().collect::<Vec<_>>(), [1, 3, 5, 7]);
Run1.54.0 · sourcepub fn into_keys(self) -> IntoKeys<K, V, A>ⓘNotable traits for IntoKeys<K, V, A>impl<K, V, A> Iterator for IntoKeys<K, V, A>where
A: Allocator + Clone, type Item = K;
pub fn into_keys(self) -> IntoKeys<K, V, A>ⓘNotable traits for IntoKeys<K, V, A>impl<K, V, A> Iterator for IntoKeys<K, V, A>where
A: Allocator + Clone, type Item = K;
A: Allocator + Clone, type Item = K;
Creates a consuming iterator visiting all the keys, in sorted order.
The map cannot be used after calling this.
The iterator element type is K
.
Examples
use std::collections::BTreeMap;
let mut a = BTreeMap::new();
a.insert(2, "b");
a.insert(1, "a");
let keys: Vec<i32> = a.into_keys().collect();
assert_eq!(keys, [1, 2]);
Run1.54.0 · sourcepub fn into_values(self) -> IntoValues<K, V, A>ⓘNotable traits for IntoValues<K, V, A>impl<K, V, A> Iterator for IntoValues<K, V, A>where
A: Allocator + Clone, type Item = V;
pub fn into_values(self) -> IntoValues<K, V, A>ⓘNotable traits for IntoValues<K, V, A>impl<K, V, A> Iterator for IntoValues<K, V, A>where
A: Allocator + Clone, type Item = V;
A: Allocator + Clone, type Item = V;
Creates a consuming iterator visiting all the values, in order by key.
The map cannot be used after calling this.
The iterator element type is V
.
Examples
use std::collections::BTreeMap;
let mut a = BTreeMap::new();
a.insert(1, "hello");
a.insert(2, "goodbye");
let values: Vec<&str> = a.into_values().collect();
assert_eq!(values, ["hello", "goodbye"]);
Runsourceimpl<K, V, A> BTreeMap<K, V, A>where
A: Allocator + Clone,
impl<K, V, A> BTreeMap<K, V, A>where
A: Allocator + Clone,
sourcepub fn iter(&self) -> Iter<'_, K, V>ⓘNotable traits for Iter<'a, K, V>impl<'a, K, V> Iterator for Iter<'a, K, V>where
K: 'a,
V: 'a, type Item = (&'a K, &'a V);
pub fn iter(&self) -> Iter<'_, K, V>ⓘNotable traits for Iter<'a, K, V>impl<'a, K, V> Iterator for Iter<'a, K, V>where
K: 'a,
V: 'a, type Item = (&'a K, &'a V);
K: 'a,
V: 'a, type Item = (&'a K, &'a V);
Gets an iterator over the entries of the map, sorted by key.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map = BTreeMap::new();
map.insert(3, "c");
map.insert(2, "b");
map.insert(1, "a");
for (key, value) in map.iter() {
println!("{key}: {value}");
}
let (first_key, first_value) = map.iter().next().unwrap();
assert_eq!((*first_key, *first_value), (1, "a"));
Runsourcepub fn iter_mut(&mut self) -> IterMut<'_, K, V>ⓘNotable traits for IterMut<'a, K, V>impl<'a, K, V> Iterator for IterMut<'a, K, V> type Item = (&'a K, &'a mut V);
pub fn iter_mut(&mut self) -> IterMut<'_, K, V>ⓘNotable traits for IterMut<'a, K, V>impl<'a, K, V> Iterator for IterMut<'a, K, V> type Item = (&'a K, &'a mut V);
Gets a mutable iterator over the entries of the map, sorted by key.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut map = BTreeMap::from([
("a", 1),
("b", 2),
("c", 3),
]);
// add 10 to the value if the key isn't "a"
for (key, value) in map.iter_mut() {
if key != &"a" {
*value += 10;
}
}
Runsourcepub fn keys(&self) -> Keys<'_, K, V>ⓘNotable traits for Keys<'a, K, V>impl<'a, K, V> Iterator for Keys<'a, K, V> type Item = &'a K;
pub fn keys(&self) -> Keys<'_, K, V>ⓘNotable traits for Keys<'a, K, V>impl<'a, K, V> Iterator for Keys<'a, K, V> type Item = &'a K;
sourcepub fn values(&self) -> Values<'_, K, V>ⓘNotable traits for Values<'a, K, V>impl<'a, K, V> Iterator for Values<'a, K, V> type Item = &'a V;
pub fn values(&self) -> Values<'_, K, V>ⓘNotable traits for Values<'a, K, V>impl<'a, K, V> Iterator for Values<'a, K, V> type Item = &'a V;
1.10.0 · sourcepub fn values_mut(&mut self) -> ValuesMut<'_, K, V>ⓘNotable traits for ValuesMut<'a, K, V>impl<'a, K, V> Iterator for ValuesMut<'a, K, V> type Item = &'a mut V;
pub fn values_mut(&mut self) -> ValuesMut<'_, K, V>ⓘNotable traits for ValuesMut<'a, K, V>impl<'a, K, V> Iterator for ValuesMut<'a, K, V> type Item = &'a mut V;
Gets a mutable iterator over the values of the map, in order by key.
Examples
Basic usage:
use std::collections::BTreeMap;
let mut a = BTreeMap::new();
a.insert(1, String::from("hello"));
a.insert(2, String::from("goodbye"));
for value in a.values_mut() {
value.push_str("!");
}
let values: Vec<String> = a.values().cloned().collect();
assert_eq!(values, [String::from("hello!"),
String::from("goodbye!")]);
RunTrait Implementations
1.2.0 · sourceimpl<'a, K, V, A> Extend<(&'a K, &'a V)> for BTreeMap<K, V, A>where
K: Ord + Copy,
V: Copy,
A: Allocator + Clone,
impl<'a, K, V, A> Extend<(&'a K, &'a V)> for BTreeMap<K, V, A>where
K: Ord + Copy,
V: Copy,
A: Allocator + Clone,
sourcefn extend<I>(&mut self, iter: I)where
I: IntoIterator<Item = (&'a K, &'a V)>,
fn extend<I>(&mut self, iter: I)where
I: IntoIterator<Item = (&'a K, &'a V)>,
sourcefn extend_one(&mut self, (&'a K, &'a V))
fn extend_one(&mut self, (&'a K, &'a V))
extend_one
#72631)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
#72631)sourceimpl<K, V, A> Extend<(K, V)> for BTreeMap<K, V, A>where
K: Ord,
A: Allocator + Clone,
impl<K, V, A> Extend<(K, V)> for BTreeMap<K, V, A>where
K: Ord,
A: Allocator + Clone,
sourcefn extend<T>(&mut self, iter: T)where
T: IntoIterator<Item = (K, V)>,
fn extend<T>(&mut self, iter: T)where
T: IntoIterator<Item = (K, V)>,
sourcefn extend_one(&mut self, (K, V))
fn extend_one(&mut self, (K, V))
extend_one
#72631)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
#72631)sourceimpl<K, Q, V, A> Index<&Q> for BTreeMap<K, V, A>where
A: Allocator + Clone,
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
impl<K, Q, V, A> Index<&Q> for BTreeMap<K, V, A>where
A: Allocator + Clone,
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
sourceimpl<'a, K, V, A> IntoIterator for &'a BTreeMap<K, V, A>where
A: Allocator + Clone,
impl<'a, K, V, A> IntoIterator for &'a BTreeMap<K, V, A>where
A: Allocator + Clone,
sourceimpl<'a, K, V, A> IntoIterator for &'a mut BTreeMap<K, V, A>where
A: Allocator + Clone,
impl<'a, K, V, A> IntoIterator for &'a mut BTreeMap<K, V, A>where
A: Allocator + Clone,
sourceimpl<K, V, A> IntoIterator for BTreeMap<K, V, A>where
A: Allocator + Clone,
impl<K, V, A> IntoIterator for BTreeMap<K, V, A>where
A: Allocator + Clone,
sourceimpl<K, V, A> Ord for BTreeMap<K, V, A>where
K: Ord,
V: Ord,
A: Allocator + Clone,
impl<K, V, A> Ord for BTreeMap<K, V, A>where
K: Ord,
V: Ord,
A: Allocator + Clone,
1.21.0 · sourceconst fn max(self, other: Self) -> Self
const fn max(self, other: Self) -> Self
1.21.0 · sourceconst fn min(self, other: Self) -> Self
const fn min(self, other: Self) -> Self
1.50.0 · sourceconst fn clamp(self, min: Self, max: Self) -> Selfwhere
Self: PartialOrd<Self>,
const fn clamp(self, min: Self, max: Self) -> Selfwhere
Self: PartialOrd<Self>,
sourceimpl<K, V, A> PartialEq<BTreeMap<K, V, A>> for BTreeMap<K, V, A>where
K: PartialEq<K>,
V: PartialEq<V>,
A: Allocator + Clone,
impl<K, V, A> PartialEq<BTreeMap<K, V, A>> for BTreeMap<K, V, A>where
K: PartialEq<K>,
V: PartialEq<V>,
A: Allocator + Clone,
sourceimpl<K, V, A> PartialOrd<BTreeMap<K, V, A>> for BTreeMap<K, V, A>where
K: PartialOrd<K>,
V: PartialOrd<V>,
A: Allocator + Clone,
impl<K, V, A> PartialOrd<BTreeMap<K, V, A>> for BTreeMap<K, V, A>where
K: PartialOrd<K>,
V: PartialOrd<V>,
A: Allocator + Clone,
sourcefn partial_cmp(&self, other: &BTreeMap<K, V, A>) -> Option<Ordering>
fn partial_cmp(&self, other: &BTreeMap<K, V, A>) -> Option<Ordering>
sourceconst fn le(&self, other: &Rhs) -> bool
const fn le(&self, other: &Rhs) -> bool
self
and other
) and is used by the <=
operator. Read more