Struct nom::lib::std::collections::btree_map::BTreeMap 1.0.0[−][src]
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 logBn) 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 alot."); // 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 book in &to_find { match movie_reviews.get(book) { Some(review) => println!("{}: {}", book, review), None => println!("{} is unreviewed.", book) } } // iterate over everything. for (movie, review) in &movie_reviews { println!("{}: \"{}\"", movie, review); }
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();
Methods
impl<K, V> BTreeMap<K, V> where
K: Ord,
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impl<K, V> BTreeMap<K, V> where
K: Ord,
pub fn new() -> BTreeMap<K, V>
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pub fn new() -> BTreeMap<K, V>
Makes a new empty BTreeMap with a reasonable choice for B.
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");
pub fn clear(&mut self)
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pub fn clear(&mut self)
Clears the map, removing all values.
Examples
Basic usage:
use std::collections::BTreeMap; let mut a = BTreeMap::new(); a.insert(1, "a"); a.clear(); assert!(a.is_empty());
pub fn get<Q>(&self, key: &Q) -> Option<&V> where
K: Borrow<Q>,
Q: Ord + ?Sized,
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pub fn get<Q>(&self, key: &Q) -> Option<&V> where
K: Borrow<Q>,
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);
pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)> where
K: Borrow<Q>,
Q: Ord + ?Sized,
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pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)> where
K: Borrow<Q>,
Q: Ord + ?Sized,
map_get_key_value
)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
#![feature(map_get_key_value)] 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);
pub fn contains_key<Q>(&self, key: &Q) -> bool where
K: Borrow<Q>,
Q: Ord + ?Sized,
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pub fn contains_key<Q>(&self, key: &Q) -> bool where
K: Borrow<Q>,
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);
pub fn get_mut<Q>(&mut self, key: &Q) -> Option<&mut V> where
K: Borrow<Q>,
Q: Ord + ?Sized,
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pub fn get_mut<Q>(&mut self, key: &Q) -> Option<&mut V> where
K: Borrow<Q>,
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");
pub fn insert(&mut self, key: K, value: V) -> Option<V>
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pub fn insert(&mut self, key: K, value: V) -> Option<V>
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");
pub fn remove<Q>(&mut self, key: &Q) -> Option<V> where
K: Borrow<Q>,
Q: Ord + ?Sized,
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pub fn remove<Q>(&mut self, key: &Q) -> Option<V> where
K: Borrow<Q>,
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);
pub fn append(&mut self, other: &mut BTreeMap<K, V>)
1.11.0[src]
pub fn append(&mut self, other: &mut BTreeMap<K, V>)
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");
ⓘImportant traits for Range<'a, K, V>pub fn range<T, R>(&self, range: R) -> Range<K, V> where
K: Borrow<T>,
R: RangeBounds<T>,
T: Ord + ?Sized,
1.17.0[src]
pub fn range<T, R>(&self, range: R) -> Range<K, V> where
K: Borrow<T>,
R: RangeBounds<T>,
T: Ord + ?Sized,
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());
ⓘImportant traits for RangeMut<'a, K, V>pub fn range_mut<T, R>(&mut self, range: R) -> RangeMut<K, V> where
K: Borrow<T>,
R: RangeBounds<T>,
T: Ord + ?Sized,
1.17.0[src]
pub fn range_mut<T, R>(&mut self, range: R) -> RangeMut<K, V> where
K: Borrow<T>,
R: RangeBounds<T>,
T: Ord + ?Sized,
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); }
pub fn entry(&mut self, key: K) -> Entry<K, V>
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pub fn entry(&mut self, key: K) -> Entry<K, V>
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);
pub fn split_off<Q>(&mut self, key: &Q) -> BTreeMap<K, V> where
K: Borrow<Q>,
Q: Ord + ?Sized,
1.11.0[src]
pub fn split_off<Q>(&mut self, key: &Q) -> BTreeMap<K, V> where
K: Borrow<Q>,
Q: Ord + ?Sized,
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");
impl<K, V> BTreeMap<K, V>
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impl<K, V> BTreeMap<K, V>
ⓘImportant traits for Iter<'a, K, V>pub fn iter(&self) -> Iter<K, V>
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pub fn iter(&self) -> Iter<K, 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"));
ⓘImportant traits for IterMut<'a, K, V>pub fn iter_mut(&mut self) -> IterMut<K, V>
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pub fn iter_mut(&mut self) -> IterMut<K, 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::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; } }
ⓘImportant traits for Keys<'a, K, V>pub fn keys(&'a self) -> Keys<'a, K, V>
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pub fn keys(&'a self) -> Keys<'a, K, V>
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]);
ⓘImportant traits for Values<'a, K, V>pub fn values(&'a self) -> Values<'a, K, V>
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pub fn values(&'a self) -> Values<'a, K, V>
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"]);
ⓘImportant traits for ValuesMut<'a, K, V>pub fn values_mut(&mut self) -> ValuesMut<K, V>
1.10.0[src]
pub fn values_mut(&mut self) -> ValuesMut<K, 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!")]);
pub fn len(&self) -> usize
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pub fn len(&self) -> usize
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);
pub fn is_empty(&self) -> bool
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pub fn is_empty(&self) -> bool
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());
Trait Implementations
impl<K, V> Default for BTreeMap<K, V> where
K: Ord,
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impl<K, V> Default for BTreeMap<K, V> where
K: Ord,
impl<K, V> FromIterator<(K, V)> for BTreeMap<K, V> where
K: Ord,
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impl<K, V> FromIterator<(K, V)> for BTreeMap<K, V> where
K: Ord,
fn from_iter<T>(iter: T) -> BTreeMap<K, V> where
T: IntoIterator<Item = (K, V)>,
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fn from_iter<T>(iter: T) -> BTreeMap<K, V> where
T: IntoIterator<Item = (K, V)>,
Creates a value from an iterator. Read more
impl<K, V> Debug for BTreeMap<K, V> where
K: Debug,
V: Debug,
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impl<K, V> Debug for BTreeMap<K, V> where
K: Debug,
V: Debug,
fn fmt(&self, f: &mut Formatter) -> Result<(), Error>
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fn fmt(&self, f: &mut Formatter) -> Result<(), Error>
Formats the value using the given formatter. Read more
impl<K, V> PartialEq<BTreeMap<K, V>> for BTreeMap<K, V> where
K: PartialEq<K>,
V: PartialEq<V>,
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impl<K, V> PartialEq<BTreeMap<K, V>> for BTreeMap<K, V> where
K: PartialEq<K>,
V: PartialEq<V>,
fn eq(&self, other: &BTreeMap<K, V>) -> bool
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fn eq(&self, other: &BTreeMap<K, V>) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, other: &Rhs) -> bool
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fn ne(&self, other: &Rhs) -> bool
This method tests for !=
.
impl<'a, K, V> Extend<(&'a K, &'a V)> for BTreeMap<K, V> where
K: Copy + Ord,
V: Copy,
1.2.0[src]
impl<'a, K, V> Extend<(&'a K, &'a V)> for BTreeMap<K, V> where
K: Copy + Ord,
V: Copy,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = (&'a K, &'a V)>,
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fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = (&'a K, &'a V)>,
Extends a collection with the contents of an iterator. Read more
impl<K, V> Extend<(K, V)> for BTreeMap<K, V> where
K: Ord,
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impl<K, V> Extend<(K, V)> for BTreeMap<K, V> where
K: Ord,
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = (K, V)>,
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fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = (K, V)>,
Extends a collection with the contents of an iterator. Read more
impl<K, V> PartialOrd<BTreeMap<K, V>> for BTreeMap<K, V> where
K: PartialOrd<K>,
V: PartialOrd<V>,
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impl<K, V> PartialOrd<BTreeMap<K, V>> for BTreeMap<K, V> where
K: PartialOrd<K>,
V: PartialOrd<V>,
fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering>
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fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, other: &Rhs) -> bool
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fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
fn le(&self, other: &Rhs) -> bool
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fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
fn gt(&self, other: &Rhs) -> bool
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fn gt(&self, other: &Rhs) -> bool
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
fn ge(&self, other: &Rhs) -> bool
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fn ge(&self, other: &Rhs) -> bool
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl<K, V> Eq for BTreeMap<K, V> where
K: Eq,
V: Eq,
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impl<K, V> Eq for BTreeMap<K, V> where
K: Eq,
V: Eq,
impl<K, V> Hash for BTreeMap<K, V> where
K: Hash,
V: Hash,
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impl<K, V> Hash for BTreeMap<K, V> where
K: Hash,
V: Hash,
fn hash<H>(&self, state: &mut H) where
H: Hasher,
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fn hash<H>(&self, state: &mut H) where
H: Hasher,
Feeds this value into the given [Hasher
]. Read more
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
1.3.0[src]
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
Feeds a slice of this type into the given [Hasher
]. Read more
impl<K, V> Drop for BTreeMap<K, V>
1.7.0[src]
impl<K, V> Drop for BTreeMap<K, V>
impl<'a, K, V> IntoIterator for &'a mut BTreeMap<K, V> where
K: 'a,
V: 'a,
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impl<'a, K, V> IntoIterator for &'a mut BTreeMap<K, V> where
K: 'a,
V: 'a,
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?
ⓘImportant traits for IterMut<'a, K, V>fn into_iter(self) -> IterMut<'a, K, V>
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fn into_iter(self) -> IterMut<'a, K, V>
Creates an iterator from a value. Read more
impl<K, V> IntoIterator for BTreeMap<K, V>
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impl<K, V> IntoIterator for BTreeMap<K, V>
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?
ⓘImportant traits for IntoIter<K, V>fn into_iter(self) -> IntoIter<K, V>
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fn into_iter(self) -> IntoIter<K, V>
Creates an iterator from a value. Read more
impl<'a, K, V> IntoIterator for &'a BTreeMap<K, V> where
K: 'a,
V: 'a,
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impl<'a, K, V> IntoIterator for &'a BTreeMap<K, V> where
K: 'a,
V: 'a,
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?
ⓘImportant traits for Iter<'a, K, V>fn into_iter(self) -> Iter<'a, K, V>
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fn into_iter(self) -> Iter<'a, K, V>
Creates an iterator from a value. Read more
impl<K, V> Ord for BTreeMap<K, V> where
K: Ord,
V: Ord,
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impl<K, V> Ord for BTreeMap<K, V> where
K: Ord,
V: Ord,
fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering
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fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering
This method returns an Ordering
between self
and other
. Read more
fn max(self, other: Self) -> Self
1.21.0[src]
fn max(self, other: Self) -> Self
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
1.21.0[src]
fn min(self, other: Self) -> Self
Compares and returns the minimum of two values. Read more
impl<'a, K, Q, V> Index<&'a Q> for BTreeMap<K, V> where
K: Ord + Borrow<Q>,
Q: Ord + ?Sized,
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impl<'a, K, Q, V> Index<&'a Q> for BTreeMap<K, V> where
K: Ord + Borrow<Q>,
Q: Ord + ?Sized,
type Output = V
The returned type after indexing.
ⓘImportant traits for &'a mut Rfn index(&self, key: &Q) -> &V
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fn index(&self, key: &Q) -> &V
Returns a reference to the value corresponding to the supplied key.
Panics
Panics if the key is not present in the BTreeMap
.
impl<K, V> Clone for BTreeMap<K, V> where
K: Clone,
V: Clone,
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impl<K, V> Clone for BTreeMap<K, V> where
K: Clone,
V: Clone,