rustymath-core 0.1.56

Numerical algorithms, formulas and compact array storage.
Documentation 
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//! The hash maps and sets rustymath uses. `Hashing` is foldhash's fast hasher with its fixed seed (`FixedState`), with `hash_one` marked `#[inline(always)]`. With one seed in every process, maps hash and iterate alike between runs, and instruction counts repeat. hashbrown 0.17 hashes every key through `BuildHasher::hash_one`, and core's default body for it has no inline hint, so incremental builds can call it out of line on every lookup.
use std::hash::{BuildHasher, Hash, Hasher};

#[derive(Clone, Default, Debug)]
pub struct Hashing(foldhash::fast::FixedState);

impl BuildHasher for Hashing {
    type Hasher = foldhash::fast::FoldHasher<'static>;
    #[inline(always)]
    fn build_hasher(&self) -> Self::Hasher { self.0.build_hasher() }
    #[inline(always)]
    fn hash_one<T: Hash>(&self, x: T) -> u64 {
        let mut h = self.build_hasher();
        x.hash(&mut h);
        h.finish()
    }
}

pub type HashMap<K, V> = hashbrown::HashMap<K, V, Hashing>;
pub type HashSet<K> = hashbrown::HashSet<K, Hashing>;

/// `new` and `with_capacity` for `HashMap`, which hashbrown gives only for its default hasher.
pub trait HashMapExt {
    fn new() -> Self;
    fn with_capacity(capacity: usize) -> Self;
}
impl<K, V> HashMapExt for HashMap<K, V> {
    fn new() -> Self { Self::with_hasher(Hashing::default()) }
    fn with_capacity(capacity: usize) -> Self { Self::with_capacity_and_hasher(capacity, Hashing::default()) }
}

/// `new` and `with_capacity` for `HashSet`, which hashbrown gives only for its default hasher.
pub trait HashSetExt {
    fn new() -> Self;
    fn with_capacity(capacity: usize) -> Self;
}
impl<K> HashSetExt for HashSet<K> {
    fn new() -> Self { Self::with_hasher(Hashing::default()) }
    fn with_capacity(capacity: usize) -> Self { Self::with_capacity_and_hasher(capacity, Hashing::default()) }
}