Counter

Simple counter library for Rust iterables. Inspired by, and largely mimicing the API of, Python's Counter.

Examples

Just count an iterable

rust let char_counts = Counter::init("barefoot".chars()); let counts_counts = Counter::init(char_counts.values());

Updates are simple

rust let mut counts = Counter::init("able babble table babble rabble table able fable scrabble".split_whitespace()); // 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 = Counter::init("scrabble cabbie fable babble".split_whitespace()); let difference = counts - other_counts;

Get the most common items

most_common_ordered() uses the natural ordering of keys which are Ord.

rust let by_common = Counter::init("eaddbbccc".chars()) .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.

rust let counter = Counter::init("eaddbbccc".chars()); 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> implements Deref<Target=HashMap<T, usize>> and DerefMut<Target=HashMap<T, usize>>, which means that you can perform any operations on it which are valid for a HashMap.

rust let mut counter = Counter::init("aa-bb-cc".chars()); counter.remove(&'-'); assert!(counter == Counter::init("aabbcc".chars()));

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.

```rust

[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), ];