Struct counter::Counter[−][src]

pub struct Counter<T: Hash + Eq, N = usize> { /* fields omitted */ }

Methods

impl<T, N> Counter<T, N> where
    T: Hash + Eq,
    N: PartialOrd + AddAssign + SubAssign + Zero + One, 
[src]

Create a new, empty Counter

Create a new Counter initialized with the given iterable

Add the counts of the elements from the given iterable to this counter

Consumes this counter and returns a HashMap mapping the items to the counts.

Remove the counts of the elements from the given iterable to this counter

Non-positive counts are automatically removed

let mut counter = "abbccc".chars().collect::<Counter<_>>();
counter.subtract("abba".chars());
let expect = [('c', 3)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(counter.into_map(), expect);

impl<T, N> Counter<T, N> where
    T: Hash + Eq + Clone,
    N: Clone + Ord, 
[src]

ⓘImportant traits for Vec<u8>

Create an iterator over (frequency, elem) pairs, sorted most to least common.

let mc = "pappaopolo".chars().collect::<Counter<_>>().most_common();
let expected = vec![('p', 4), ('o', 3), ('a', 2), ('l', 1)];
assert_eq!(mc, expected);

Note that the ordering of duplicates is unstable.

ⓘImportant traits for Vec<u8>

Create an iterator over (frequency, elem) pairs, sorted most to least common.

In the event that two keys have an equal frequency, use the supplied ordering function to further arrange the results.

For example, we can sort reverse-alphabetically:

let counter = "eaddbbccc".chars().collect::<Counter<_>>();
let by_common = counter.most_common_tiebreaker(|&a, &b| b.cmp(&a));
let expected = vec![('c', 3), ('d', 2), ('b', 2), ('e', 1), ('a', 1)];
assert_eq!(by_common, expected);

impl<T, N> Counter<T, N> where
    T: Hash + Eq + Clone + Ord,
    N: Clone + Ord, 
[src]

ⓘImportant traits for Vec<u8>

Create an iterator over (frequency, elem) pairs, sorted most to least common.

In the event that two keys have an equal frequency, use the natural ordering of the keys to further sort the results.

let mc = "abracadabra".chars().collect::<Counter<_>>().most_common_ordered();
let expect = vec![('a', 5), ('b', 2), ('r', 2), ('c', 1), ('d', 1)];
assert_eq!(mc, expect);

Methods from Deref<Target = HashMap<T, N>>

ⓘImportant traits for &'a mut R

Returns a reference to the map's BuildHasher.

Examples

use std::collections::HashMap;
use std::collections::hash_map::RandomState;

let hasher = RandomState::new();
let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
let hasher: &RandomState = map.hasher();

Returns the number of elements the map can hold without reallocating.

This number is a lower bound; the HashMap<K, V> might be able to hold more, but is guaranteed to be able to hold at least this many.

Examples

use std::collections::HashMap;
let map: HashMap<i32, i32> = HashMap::with_capacity(100);
assert!(map.capacity() >= 100);

Reserves capacity for at least additional more elements to be inserted in the HashMap. The collection may reserve more space to avoid frequent reallocations.

Panics

Panics if the new allocation size overflows usize.

Examples

use std::collections::HashMap;
let mut map: HashMap<&str, i32> = HashMap::new();
map.reserve(10);

🔬 This is a nightly-only experimental API. (try_reserve)

new API

Tries to reserve capacity for at least additional more elements to be inserted in the given HashMap<K,V>. The collection may reserve more space to avoid frequent reallocations.

Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

Examples

#![feature(try_reserve)]
use std::collections::HashMap;
let mut map: HashMap<&str, isize> = HashMap::new();
map.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");

Shrinks the capacity of the map as much as possible. It will drop down as much as possible while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Examples

use std::collections::HashMap;

let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
map.insert(1, 2);
map.insert(3, 4);
assert!(map.capacity() >= 100);
map.shrink_to_fit();
assert!(map.capacity() >= 2);

🔬 This is a nightly-only experimental API. (shrink_to)

new API

Shrinks the capacity of the map with a lower limit. It will drop down no lower than the supplied limit while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Panics if the current capacity is smaller than the supplied minimum capacity.

Examples

#![feature(shrink_to)]
use std::collections::HashMap;

let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
map.insert(1, 2);
map.insert(3, 4);
assert!(map.capacity() >= 100);
map.shrink_to(10);
assert!(map.capacity() >= 10);
map.shrink_to(0);
assert!(map.capacity() >= 2);

ⓘImportant traits for Keys<'a, K, V>

An iterator visiting all keys in arbitrary order. The iterator element type is &'a K.

Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

for key in map.keys() {
    println!("{}", key);
}

ⓘImportant traits for Values<'a, K, V>

An iterator visiting all values in arbitrary order. The iterator element type is &'a V.

Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

for val in map.values() {
    println!("{}", val);
}

ⓘImportant traits for ValuesMut<'a, K, V>

An iterator visiting all values mutably in arbitrary order. The iterator element type is &'a mut V.

Examples

use std::collections::HashMap;

let mut map = HashMap::new();

map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

for val in map.values_mut() {
    *val = *val + 10;
}

for val in map.values() {
    println!("{}", val);
}

ⓘImportant traits for Iter<'a, K, V>

An iterator visiting all key-value pairs in arbitrary order. The iterator element type is (&'a K, &'a V).

Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

for (key, val) in map.iter() {
    println!("key: {} val: {}", key, val);
}

ⓘImportant traits for IterMut<'a, K, V>

An iterator visiting all key-value pairs in arbitrary order, with mutable references to the values. The iterator element type is (&'a K, &'a mut V).

Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

// Update all values
for (_, val) in map.iter_mut() {
    *val *= 2;
}

for (key, val) in &map {
    println!("key: {} val: {}", key, val);
}

Gets the given key's corresponding entry in the map for in-place manipulation.

Examples

use std::collections::HashMap;

let mut letters = HashMap::new();

for ch in "a short treatise on fungi".chars() {
    let counter = letters.entry(ch).or_insert(0);
    *counter += 1;
}

assert_eq!(letters[&'s'], 2);
assert_eq!(letters[&'t'], 3);
assert_eq!(letters[&'u'], 1);
assert_eq!(letters.get(&'y'), None);

Returns the number of elements in the map.

Examples

use std::collections::HashMap;

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

Returns true if the map contains no elements.

Examples

use std::collections::HashMap;

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

ⓘImportant traits for Drain<'a, K, V>

Clears the map, returning all key-value pairs as an iterator. Keeps the allocated memory for reuse.

Examples

use std::collections::HashMap;

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

for (k, v) in a.drain().take(1) {
    assert!(k == 1 || k == 2);
    assert!(v == "a" || v == "b");
}

assert!(a.is_empty());

Clears the map, removing all key-value pairs. Keeps the allocated memory for reuse.

Examples

use std::collections::HashMap;

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

Returns a reference to the value corresponding to the key.

The key may be any borrowed form of the map's key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get(&1), Some(&"a"));
assert_eq!(map.get(&2), None);

🔬 This is a nightly-only experimental API. (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 Hash and Eq on the borrowed form must match those for the key type.

Examples

#![feature(map_get_key_value)]
use std::collections::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
assert_eq!(map.get_key_value(&2), None);

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 Hash and Eq on the borrowed form must match those for the key type.

Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&2), false);

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 Hash and Eq on the borrowed form must match those for the key type.

Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
if let Some(x) = map.get_mut(&1) {
    *x = "b";
}
assert_eq!(map[&1], "b");

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

use std::collections::HashMap;

let mut map = HashMap::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");

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 Hash and Eq on the borrowed form must match those for the key type.

Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.remove(&1), Some("a"));
assert_eq!(map.remove(&1), None);

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 Hash and Eq on the borrowed form must match those for the key type.

Examples

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.remove_entry(&1), Some((1, "a")));
assert_eq!(map.remove(&1), None);

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

use std::collections::HashMap;

let mut map: HashMap<i32, i32> = (0..8).map(|x|(x, x*10)).collect();
map.retain(|&k, _| k % 2 == 0);
assert_eq!(map.len(), 4);

Trait Implementations

impl<T: Clone + Hash + Eq, N: Clone> Clone for Counter<T, N>
[src]

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl<T: PartialEq + Hash + Eq, N: PartialEq> PartialEq for Counter<T, N>
[src]

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

impl<T: Eq + Hash + Eq, N: Eq> Eq for Counter<T, N>
[src]

impl<T: Debug + Hash + Eq, N: Debug> Debug for Counter<T, N>
[src]

Formats the value using the given formatter. Read more

impl<T: Default + Hash + Eq, N: Default> Default for Counter<T, N>
[src]

Returns the "default value" for a type. Read more

impl<T, N> AddAssign for Counter<T, N> where
    T: Clone + Hash + Eq,
    N: Clone + Zero + AddAssign, 
[src]

Add another counter to this counter

c += d; -> c[x] += d[x] for all x

let mut c = "aaab".chars().collect::<Counter<_>>();
let d = "abb".chars().collect::<Counter<_>>();

c += d;

let expect = [('a', 4), ('b', 3)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(c.into_map(), expect);

impl<T, N> Add for Counter<T, N> where
    T: Clone + Hash + Eq,
    N: Clone + PartialOrd + PartialEq + AddAssign + Zero, 
[src]

The resulting type after applying the + operator.

Add two counters together.

out = c + d; -> out[x] == c[x] + d[x] for all x

let c = "aaab".chars().collect::<Counter<_>>();
let d = "abb".chars().collect::<Counter<_>>();

let e = c + d;

let expect = [('a', 4), ('b', 3)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(e.into_map(), expect);

impl<T, N> SubAssign for Counter<T, N> where
    T: Hash + Eq,
    N: Clone + PartialOrd + PartialEq + SubAssign + Zero, 
[src]

Subtract (keeping only positive values).

c -= d; -> c[x] -= d[x] for all x, keeping only items with a value greater than N::zero().

let mut c = "aaab".chars().collect::<Counter<_>>();
let d = "abb".chars().collect::<Counter<_>>();

c -= d;

let expect = [('a', 2)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(c.into_map(), expect);

impl<T, N> Sub for Counter<T, N> where
    T: Hash + Eq,
    N: Clone + PartialOrd + PartialEq + SubAssign + Zero, 
[src]

The resulting type after applying the - operator.

Subtract (keeping only positive values).

out = c - d; -> out[x] == c[x] - d[x] for all x, keeping only items with a value greater than N::zero().

let c = "aaab".chars().collect::<Counter<_>>();
let d = "abb".chars().collect::<Counter<_>>();

let e = c - d;

let expect = [('a', 2)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(e.into_map(), expect);

impl<T, N> BitAnd for Counter<T, N> where
    T: Clone + Hash + Eq,
    N: Clone + Ord + AddAssign + SubAssign + Zero + One, 
[src]

The resulting type after applying the & operator.

Intersection

out = c & d; -> out[x] == min(c[x], d[x])

let c = "aaab".chars().collect::<Counter<_>>();
let d = "abb".chars().collect::<Counter<_>>();

let e = c & d;

let expect = [('a', 1), ('b', 1)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(e.into_map(), expect);

impl<T, N> BitOr for Counter<T, N> where
    T: Clone + Hash + Eq,
    N: Clone + Ord + Zero, 
[src]

The resulting type after applying the | operator.

Union

out = c | d; -> out[x] == max(c[x], d[x])

let c = "aaab".chars().collect::<Counter<_>>();
let d = "abb".chars().collect::<Counter<_>>();

let e = c | d;

let expect = [('a', 3), ('b', 2)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(e.into_map(), expect);

impl<T, N> Deref for Counter<T, N> where
    T: Hash + Eq,
    N: Clone, 
[src]

The resulting type after dereferencing.

Dereferences the value.

impl<T, N> DerefMut for Counter<T, N> where
    T: Hash + Eq,
    N: Clone, 
[src]

Mutably dereferences the value.

impl<I, T, N> AddAssign<I> for Counter<T, N> where
    I: IntoIterator<Item = T>,
    T: Hash + Eq,
    N: PartialOrd + AddAssign + SubAssign + Zero + One, 
[src]

Directly add the counts of the elements of I to self

let mut counter = Counter::init("abbccc".chars());

counter += "aeeeee".chars();
let expected: HashMap<char, usize> = [('a', 2), ('b', 2), ('c', 3), ('e', 5)]
    .iter().cloned().collect();
assert_eq!(counter.into_map(), expected);

impl<I, T, N> Add<I> for Counter<T, N> where
    I: IntoIterator<Item = T>,
    T: Hash + Eq,
    N: PartialOrd + AddAssign + SubAssign + Zero + One, 
[src]

The resulting type after applying the + operator.

Consume self producing a Counter like self updated with the counts of the elements of I.

let counter = Counter::init("abbccc".chars());

let new_counter = counter + "aeeeee".chars();
let expected: HashMap<char, usize> = [('a', 2), ('b', 2), ('c', 3), ('e', 5)]
    .iter().cloned().collect();
assert_eq!(new_counter.into_map(), expected);

impl<I, T, N> SubAssign<I> for Counter<T, N> where
    I: IntoIterator<Item = T>,
    T: Hash + Eq,
    N: PartialOrd + AddAssign + SubAssign + Zero + One, 
[src]

Directly subtract the counts of the elements of I from self, keeping only items with a value greater than N::zero().

let mut c = "aaab".chars().collect::<Counter<_>>();
c -= "abb".chars();

let expect = [('a', 2)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(c.into_map(), expect);

impl<I, T, N> Sub<I> for Counter<T, N> where
    I: IntoIterator<Item = T>,
    T: Clone + Hash + Eq,
    N: Clone + PartialOrd + AddAssign + SubAssign + Zero + One, 
[src]

The resulting type after applying the - operator.

Consume self producing a Counter like self with the counts of the elements of I subtracted, keeping only positive values.

let c = "aaab".chars().collect::<Counter<_>>();
let e = c - "abb".chars();

let expect = [('a', 2)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(e.into_map(), expect);

impl<T, N> FromIterator<T> for Counter<T, N> where
    T: Hash + Eq,
    N: PartialOrd + AddAssign + SubAssign + Zero + One, 
[src]

Produce a Counter from an iterator of items. This is called automatically by iter.collect().

let counter = "abbccc".chars().collect::<Counter<_>>();
let expect = [('a', 1), ('b', 2), ('c', 3)].iter().cloned().collect::<HashMap<_, _>>();
assert_eq!(counter.into_map(), expect);

impl<T, N> FromIterator<(T, N)> for Counter<T, N> where
    T: Hash + Eq,
    N: PartialOrd + AddAssign + SubAssign + Zero + One, 
[src]

from_iter creates a counter from (item, count) tuples.

The counts of duplicate items are summed.

let counter = [('a', 1), ('b', 2), ('c', 3), ('a', 4)].iter()
    .cloned().collect::<Counter<_>>();
let expect = [('a', 5), ('b', 2), ('c', 3)].iter()
    .cloned().collect::<HashMap<_, _>>();
assert_eq!(counter.into_map(), expect);

Auto Trait Implementations

impl<T, N> Send for Counter<T, N> where
    N: Send,
    T: Send, 

impl<T, N> Sync for Counter<T, N> where
    N: Sync,
    T: Sync,