Crate counter[−][src]
Counter counts recurrent elements of iterables. It is based on the Python implementation.
The struct Counter
is the entry-point type for this module.
Examples
Just count an iterable
use counter::Counter; let char_counts = "barefoot".chars().collect::<Counter<_>>(); let counts_counts = char_counts.values().collect::<Counter<_>>();
Update a count
let mut counts = "able babble table babble rabble table able fable scrabble" .split_whitespace().collect::<Counter<_>>(); // add or subtract an iterable of the same type counts += "cain and abel fable table cable".split_whitespace(); // or add or subtract from another Counter of the same type let other_counts = "scrabble cabbie fable babble" .split_whitespace().collect::<Counter<_>>(); let difference = counts - other_counts;
Get the most common items
most_common_ordered()
uses the natural ordering of keys which are Ord
.
let by_common = "eaddbbccc".chars().collect::<Counter<_>>().most_common_ordered(); let expected = vec![('c', 3), ('b', 2), ('d', 2), ('a', 1), ('e', 1)]; assert!(by_common == expected);
Get the most common items using your own ordering
For example, here we break ties 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!(by_common == expected);
Treat it like a Map
Counter<T, N>
implements Deref<Target=HashMap<T, N>>
and
DerefMut<Target=HashMap<T, N>>
, which means that you can perform any operations
on it which are valid for a HashMap
.
let mut counter = "aa-bb-cc".chars().collect::<Counter<_>>(); counter.remove(&'-'); assert!(counter == "aabbcc".chars().collect::<Counter<_>>());
Advanced Usage
Count any iterable which is Hash + Eq
You can't use the most_common*
functions unless T is also Clone
, but simple counting works fine on a minimal data type.
#[derive(Debug, Hash, PartialEq, Eq)] struct Inty { i: usize, } impl Inty { pub fn new(i: usize) -> Inty { Inty { i: i } } } // <https://en.wikipedia.org/wiki/867-5309/Jenny> let intys = vec![ Inty::new(8), Inty::new(0), Inty::new(0), Inty::new(8), Inty::new(6), Inty::new(7), Inty::new(5), Inty::new(3), Inty::new(0), Inty::new(9), ]; let inty_counts = intys.iter().collect::<Counter<_>>(); println!("{:?}", inty_counts); // {Inty { i: 8 }: 2, Inty { i: 0 }: 3, Inty { i: 9 }: 1, Inty { i: 3 }: 1, // Inty { i: 7 }: 1, Inty { i: 6 }: 1, Inty { i: 5 }: 1} assert!(inty_counts.get(&Inty { i: 8 }) == Some(&2)); assert!(inty_counts.get(&Inty { i: 0 }) == Some(&3)); assert!(inty_counts.get(&Inty { i: 6 }) == Some(&1));
Use your own type for the count
Sometimes usize
just isn't enough. If you find yourself overflowing your
machine's native size, you can use your own type. Here, we use an i8
, but
you can use most numeric types, including bignums, as necessary.
let counter: Counter<_, i8> = "abbccc".chars().collect(); let expected: HashMap<char, i8> = [('a', 1), ('b', 2), ('c', 3)].iter().cloned().collect(); assert!(counter.into_map() == expected);
Structs
Counter |