itertools/
group_map.rs

1#![cfg(feature = "use_std")]
2
3use std::collections::HashMap;
4use std::hash::Hash;
5use std::iter::Iterator;
6
7/// Return a `HashMap` of keys mapped to a list of their corresponding values.
8///
9/// See [`.into_group_map()`](crate::Itertools::into_group_map)
10/// for more information.
11pub fn into_group_map<I, K, V>(iter: I) -> HashMap<K, Vec<V>>
12    where I: Iterator<Item=(K, V)>,
13          K: Hash + Eq,
14{
15    let mut lookup = HashMap::new();
16
17    iter.for_each(|(key, val)| {
18        lookup.entry(key).or_insert_with(Vec::new).push(val);
19    });
20
21    lookup
22}
23
24pub fn into_group_map_by<I, K, V>(iter: I, f: impl Fn(&V) -> K) -> HashMap<K, Vec<V>>
25    where
26        I: Iterator<Item=V>,
27        K: Hash + Eq,
28{
29    into_group_map(
30        iter.map(|v| (f(&v), v))
31    )
32}
itertools/group_map.rs

itertools/
group_map.rs
