1 unstable release
0.1.0 | Jun 26, 2024 |
---|
#659 in HTTP server
168 downloads per month
Used in 21 crates
(2 directly)
11KB
128 lines
Algebraic traits
A selection of traits representing abstract algebras. These can be used to abstract over types that have differing concepts of 'combination'.
Examples
Consider the following function to combine maps:
use std::hash::Hash;
use std::collections::{HashMap, HashSet};
use swimos_algebra::Semigroup;
fn combine_maps<K: Eq + Hash + Clone, T: Semigroup>(
mut left: HashMap<K, T>,
mut right: HashMap<K, T>) -> HashMap<K, T> {
let keys = left.keys().chain(right.keys()).cloned().collect::<HashSet<_>>();
keys.into_iter().filter_map(|k| {
match (left.remove(&k), right.remove(&k)) {
(None, Some(r)) => Some((k, r)),
(Some(l), None) => Some((k, l)),
(Some(l), Some(r)) => Some((k, Semigroup::op(l, r))),
_ => None,
}
}).collect()
}
This can be applied to a map with integer values,
#
#
#
let left_ints = [("red", 3), ("green", 23), ("blue", 1)]
.into_iter()
.collect::<HashMap<_, _>>();
let right_ints = [("red", 4), ("blue", 1)]
.into_iter()
.collect::<HashMap<_, _>>();
let expected_ints = [("red", 7), ("green", 23), ("blue", 2)]
.into_iter()
.collect::<HashMap<_, _>>();
assert_eq!(combine_maps(left_ints, right_ints), expected_ints);
or a map with vectors as values:
#
#
#
let left_vecs = [
("red", vec![12, -5, 6]),
("green", vec![1]),
("blue", vec![5, 8, 11]),
]
.into_iter()
.collect::<HashMap<_, _>>();
let right_vecs = [
("red", vec![4, 1]),
("blue", vec![-7])
]
.into_iter()
.collect::<HashMap<_, _>>();
let expected_vecs = [
("red", vec![12, -5, 6, 4, 1]),
("green", vec![1]),
("blue", vec![5, 8, 11, -7]),
]
.into_iter()
.collect::<HashMap<_, _>>();
assert_eq!(combine_maps(left_vecs, right_vecs), expected_vecs);