# 1.0.0[−][src]Struct std::collections::btree_map::BTreeMap

    pub struct BTreeMap<K, V> { /* fields omitted */ }

A 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 O(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.

# 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!("{} is unreviewed.", movie)
        }
    }

    // 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);
    }

Run

`BTreeMap` also implements an `Entry API`, which allows for more 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();

Run

## Implementations

### `impl<K, V> BTreeMap<K, V> where
K: Ord,` [src]

#### `pub fn new() -> BTreeMap<K, V>`[src]

Makes a new, empty `BTreeMap`.

Does not allocate anything on its own.

# Examples

Basic usage:

    use std::collections::BTreeMap;

    let mut map = BTreeMap::new();

    // entries can now be inserted into the empty map
    map.insert(1, "a");

Run

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

Clears the map, removing all elements.

# Examples

Basic usage:

    use std::collections::BTreeMap;

    let mut a = BTreeMap::new();
    a.insert(1, "a");
    a.clear();
    assert!(a.is_empty());

Run

#### `pub fn get<Q>(&self, key: &Q) -> Option<&V> where
K: Borrow<Q>,
Q: Ord + ?Sized,` [src]

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);

Run

#### `pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)> where
K: Borrow<Q>,
Q: Ord + ?Sized,` 1.40.0[src]

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);

Run

#### `pub fn first_key_value(&self) -> Option<(&K, &V)>`[src]

🔬 This is a nightly-only experimental API. (`map_first_last` #62924)

Returns the first key-value pair in the map. The key in this pair is the minimum key in the map.

# Examples

Basic usage:

    #![feature(map_first_last)]
    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")));

Run

#### `pub fn first_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>>`[src]

🔬 This is a nightly-only experimental API. (`map_first_last` #62924)

Returns the first entry in the map for in-place manipulation. The key of this entry is the minimum key in the map.

# Examples

    #![feature(map_first_last)]
    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");

Run

#### `pub fn pop_first(&mut self) -> Option<(K, V)>`[src]

🔬 This is a nightly-only experimental API. (`map_first_last` #62924)

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.

    #![feature(map_first_last)]
    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());

Run

#### `pub fn last_key_value(&self) -> Option<(&K, &V)>`[src]

🔬 This is a nightly-only experimental API. (`map_first_last` #62924)

Returns the last key-value pair in the map. The key in this pair is the maximum key in the map.

# Examples

Basic usage:

    #![feature(map_first_last)]
    use std::collections::BTreeMap;

    let mut map = BTreeMap::new();
    map.insert(1, "b");
    map.insert(2, "a");
    assert_eq!(map.last_key_value(), Some((&2, &"a")));

Run

#### `pub fn last_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>>`[src]

🔬 This is a nightly-only experimental API. (`map_first_last` #62924)

Returns the last entry in the map for in-place manipulation. The key of this entry is the maximum key in the map.

# Examples

    #![feature(map_first_last)]
    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");

Run

#### `pub fn pop_last(&mut self) -> Option<(K, V)>`[src]

🔬 This is a nightly-only experimental API. (`map_first_last` #62924)

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.

    #![feature(map_first_last)]
    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());

Run

#### `pub fn contains_key<Q>(&self, key: &Q) -> bool where
K: Borrow<Q>,
Q: Ord + ?Sized,` [src]

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);

Run

#### `pub fn get_mut<Q>(&mut self, key: &Q) -> Option<&mut V> where
K: Borrow<Q>,
Q: Ord + ?Sized,` [src]

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");

Run

#### `pub fn insert(&mut self, key: K, value: V) -> Option<V>`[src]

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");

Run

#### `pub fn remove<Q>(&mut self, key: &Q) -> Option<V> where
K: Borrow<Q>,
Q: Ord + ?Sized,` [src]

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);

Run

#### `pub fn remove_entry<Q>(&mut self, key: &Q) -> Option<(K, V)> where
K: Borrow<Q>,
Q: Ord + ?Sized,` 1.45.0[src]

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);

Run

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

🔬 This is a nightly-only experimental API. (`btree_retain` #79025)

Retains only the elements specified by the predicate.

In other words, remove all pairs `(k, v)` such that `f(&k, &mut v)` returns `false`.

# Examples

    #![feature(btree_retain)]
    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)]));

Run

#### `pub fn append(&mut self, other: &mut BTreeMap<K, V>)`1.11.0[src]

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");

Run

#### `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
K: Borrow<T>,
R: RangeBounds<T>,
T: Ord + ?Sized,` 1.17.0[src]

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());

Run

#### `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
K: Borrow<T>,
R: RangeBounds<T>,
T: Ord + ?Sized,` 1.17.0[src]

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", "Bob", "Carol", "Cheryl"]
        .iter()
        .map(|&s| (s, 0))
        .collect();
    for (_, balance) in map.range_mut("B".."Cheryl") {
        *balance += 100;
    }
    for (name, balance) in &map {
        println!("{} => {}", name, balance);
    }

Run

#### `pub fn entry(&mut self, key: K) -> Entry<'_, K, V>`[src]

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 vec!["a", "b", "a", "c", "a", "b"] {
        *count.entry(x).or_insert(0) += 1;
    }

    assert_eq!(count["a"], 3);

Run

#### `pub fn split_off<Q>(&mut self, key: &Q) -> BTreeMap<K, V> where
K: Borrow<Q>,
Q: Ord + ?Sized,` 1.11.0[src]

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");

Run

#### `pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F>ⓘ

### Notable traits for DrainFilter<'_, K, V, F>

`impl<'_, K, V, F> Iterator for DrainFilter<'_, K, V, F> where
F: FnMut(&K, &mut V) -> bool, type Item = (K, V);`
where
F: FnMut(&K, &mut V) -> bool,` [src]

🔬 This is a nightly-only experimental API. (`btree_drain_filter` #70530)

Creates an iterator which 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.

Note that `drain_filter` lets you mutate every value in the filter 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 will still be subjected to the closure and removed and dropped if it returns true.

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<_>>(), vec![0, 2, 4, 6]);
    assert_eq!(odds.keys().copied().collect::<Vec<_>>(), vec![1, 3, 5, 7]);

Run

#### `pub fn into_keys(self) -> IntoKeys<K, V>ⓘ

### Notable traits for IntoKeys<K, V>

`impl<K, V> Iterator for IntoKeys<K, V> type Item = K;`
`[src]

🔬 This is a nightly-only experimental API. (`map_into_keys_values` #75294)

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

    #![feature(map_into_keys_values)]
    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]);

Run

#### `pub fn into_values(self) -> IntoValues<K, V>ⓘ

### Notable traits for IntoValues<K, V>

`impl<K, V> Iterator for IntoValues<K, V> type Item = V;`
`[src]

🔬 This is a nightly-only experimental API. (`map_into_keys_values` #75294)

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

    #![feature(map_into_keys_values)]
    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"]);

Run

### `impl<K, V> BTreeMap<K, V>`[src]

#### `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);`
`[src]

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"));

Run

#### `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> where
K: 'a,
V: 'a, type Item = (&'a K, &'a mut V);`
`[src]

Gets a mutable iterator over the entries of the map, sorted by key.

# Examples

Basic usage:

    use std::collections::BTreeMap;

    let mut map = BTreeMap::new();
    map.insert("a", 1);
    map.insert("b", 2);
    map.insert("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;
        }
    }

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#### `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;`
`[src]

Gets an iterator over the keys of the map, in sorted order.

# Examples

Basic usage:

    use std::collections::BTreeMap;

    let mut a = BTreeMap::new();
    a.insert(2, "b");
    a.insert(1, "a");

    let keys: Vec<_> = a.keys().cloned().collect();
    assert_eq!(keys, [1, 2]);

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#### `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;`
`[src]

Gets an 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, "hello");
    a.insert(2, "goodbye");

    let values: Vec<&str> = a.values().cloned().collect();
    assert_eq!(values, ["hello", "goodbye"]);

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#### `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;`
`1.10.0[src]

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!")]);

Run

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

Returns the number of elements in the map.

# Examples

Basic usage:

    use std::collections::BTreeMap;

    let mut a = BTreeMap::new();
    assert_eq!(a.len(), 0);
    a.insert(1, "a");
    assert_eq!(a.len(), 1);

Run

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

Returns `true` if the map contains no elements.

# Examples

Basic usage:

    use std::collections::BTreeMap;

    let mut a = BTreeMap::new();
    assert!(a.is_empty());
    a.insert(1, "a");
    assert!(!a.is_empty());

Run

## Trait Implementations

### `impl<K, V> Clone for BTreeMap<K, V> where
K: Clone,
V: Clone,` [src]

#### `pub fn clone(&self) -> BTreeMap<K, V>`[src]

Returns a copy of the value. Read more

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

Performs copy-assignment from `source`. Read more

### `impl<K, V> Debug for BTreeMap<K, V> where
K: Debug,
V: Debug,` [src]

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

Formats the value using the given formatter. Read more

### `impl<K, V> Default for BTreeMap<K, V> where
K: Ord,` [src]

#### `pub fn default() -> BTreeMap<K, V>`[src]

Creates an empty `BTreeMap`.

### `impl<K, V> Drop for BTreeMap<K, V>`1.7.0[src]

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

Executes the destructor for this type. Read more

### `impl<K, V> Eq for BTreeMap<K, V> where
K: Eq,
V: Eq,` [src]

### `impl<'a, K, V> Extend<(&'a K, &'a V)> for BTreeMap<K, V> where
K: Ord + Copy,
V: Copy,` 1.2.0[src]

#### `pub fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = (&'a K, &'a V)>,` [src]

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

#### `pub fn extend_one(&mut self, (&'a K, &'a V))`[src]

🔬 This is a nightly-only experimental API. (`extend_one` #72631)

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` #72631)

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

### `impl<K, V> Extend<(K, V)> for BTreeMap<K, V> where
K: Ord,` [src]

#### `pub fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = (K, V)>,` [src]

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

#### `pub fn extend_one(&mut self, (K, V))`[src]

🔬 This is a nightly-only experimental API. (`extend_one` #72631)

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` #72631)

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

### `impl<K, V> FromIterator<(K, V)> for BTreeMap<K, V> where
K: Ord,` [src]

#### `pub fn from_iter<T>(iter: T) -> BTreeMap<K, V> where
T: IntoIterator<Item = (K, V)>,` [src]

Creates a value from an iterator. Read more

### `impl<K, V> Hash for BTreeMap<K, V> where
K: Hash,
V: Hash,` [src]

#### `pub fn hash<H>(&self, state: &mut H) where
H: Hasher,` [src]

Feeds this value into the given `Hasher`. Read more

#### `pub fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,` 1.3.0[src]

Feeds a slice of this type into the given `Hasher`. Read more

### `impl<'_, K, Q, V> Index<&'_ Q> for BTreeMap<K, V> where
K: Ord + Borrow<Q>,
Q: Ord + ?Sized,` [src]

#### `type Output = V`

The returned type after indexing.

#### `pub fn index(&self, key: &Q) -> &Vⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W`
`[src]

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

# Panics

Panics if the key is not present in the `BTreeMap`.

### `impl<'a, K, V> IntoIterator for &'a BTreeMap<K, V>`[src]

#### `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?

#### `pub fn into_iter(self) -> Iter<'a, 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);`
`[src]

Creates an iterator from a value. Read more

### `impl<'a, K, V> IntoIterator for &'a mut BTreeMap<K, V>`[src]

#### `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?

#### `pub fn into_iter(self) -> IterMut<'a, K, V>ⓘ

### Notable traits for IterMut<'a, K, V>

`impl<'a, K, V> Iterator for IterMut<'a, K, V> where
K: 'a,
V: 'a, type Item = (&'a K, &'a mut V);`
`[src]

Creates an iterator from a value. Read more

### `impl<K, V> IntoIterator for BTreeMap<K, V>`[src]

#### `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?

#### `pub fn into_iter(self) -> IntoIter<K, V>ⓘ

### Notable traits for IntoIter<K, V>

`impl<K, V> Iterator for IntoIter<K, V> type Item = (K, V);`
`[src]

Creates an iterator from a value. Read more

### `impl<K, V> Ord for BTreeMap<K, V> where
K: Ord,
V: Ord,` [src]

#### `pub fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering`[src]

This method returns an `Ordering` between `self` and `other`. Read more

#### `#[must_use]pub fn max(self, other: Self) -> Self` 1.21.0[src]

Compares and returns the maximum of two values. Read more

#### `#[must_use]pub fn min(self, other: Self) -> Self` 1.21.0[src]

Compares and returns the minimum of two values. Read more

#### `#[must_use]pub fn clamp(self, min: Self, max: Self) -> Self` 1.50.0[src]

Restrict a value to a certain interval. Read more

### `impl<K, V> PartialEq<BTreeMap<K, V>> for BTreeMap<K, V> where
K: PartialEq<K>,
V: PartialEq<V>,` [src]

#### `pub fn eq(&self, other: &BTreeMap<K, V>) -> 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`[src]

This method tests for `!=`.

### `impl<K, V> PartialOrd<BTreeMap<K, V>> for BTreeMap<K, V> where
K: PartialOrd<K>,
V: PartialOrd<V>,` [src]

#### `pub fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering>`[src]

This method returns an ordering between `self` and `other` values if one exists. Read more

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

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more

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

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more

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

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more

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

This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more

## Auto Trait Implementations

### `impl<K, V> RefUnwindSafe for BTreeMap<K, V> where
K: RefUnwindSafe,
V: RefUnwindSafe,`

### `impl<K, V> Send for BTreeMap<K, V> where
K: Send,
V: Send,`

### `impl<K, V> Sync for BTreeMap<K, V> where
K: Sync,
V: Sync,`

### `impl<K, V> Unpin for BTreeMap<K, V>`

### `impl<K, V> UnwindSafe for BTreeMap<K, V> where
K: RefUnwindSafe,
V: RefUnwindSafe,`

## 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ⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W`
`[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ⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W`
`[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` #41263)

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.