feat(variadics): add variadic hash set

variadics/Cargo.toml

@@ -12,6 +12,7 @@ workspace = true
 
 [dependencies]
 sealed = "0.5.0"
+hashbrown = "0.14.0"
 
 [dev-dependencies]
 trybuild = "1.0"

variadics/src/hash_set.rs

@@ -0,0 +1,76 @@
+use std::hash::{BuildHasher, Hash, Hasher, RandomState};
+
+use hashbrown::hash_table::Entry;
+use hashbrown::HashTable;
+
+use crate::{PartialEqVariadic, VariadicExt};
+
+pub struct VariadicHashSet<T, S = RandomState> {
+    table: HashTable<T>,
+    hasher: S,
+}
+impl<T> VariadicHashSet<T> {
+    pub fn new() -> Self {
+        Self {
+            table: HashTable::new(),
+            hasher: RandomState::default(),
+        }
+    }
+}
+impl<T, S> VariadicHashSet<T, S>
+where
+    T: VariadicExt + PartialEqVariadic,
+    for<'a> T::AsRefVar<'a>: Hash,
+    S: BuildHasher,
+{
+    fn get_hash(hasher: &S, ref_var: T::AsRefVar<'_>) -> u64 {
+        let mut hasher = hasher.build_hasher();
+        ref_var.hash(&mut hasher);
+        hasher.finish()
+    }
+
+    pub fn get<'a>(&'a self, ref_var: T::AsRefVar<'_>) -> Option<&'a T> {
+        let hash = Self::get_hash(&self.hasher, ref_var);
+        self.table.find(hash, |item| {
+            <T as PartialEqVariadic>::eq_ref(ref_var, item.as_ref_var())
+        })
+    }
+
+    pub fn insert(&mut self, element: T) -> bool {
+        let hash = Self::get_hash(&self.hasher, element.as_ref_var());
+        let entry = self.table.entry(
+            hash,
+            |item| <T as PartialEqVariadic>::eq(&element, &item),
+            |item| Self::get_hash(&self.hasher, item.as_ref_var()),
+        );
+        match entry {
+            Entry::Occupied(_occupied_entry) => false,
+            Entry::Vacant(vacant_entry) => {
+                vacant_entry.insert(element);
+                true
+            },
+        }
+    }
+
+    pub fn len(&self) -> usize {
+        self.table.len()
+    }
+
+    pub fn iter<'a>(&'a self) -> impl Iterator<Item = T::AsRefVar<'a>> {
+        self.table.iter().map(|item| item.as_ref_var())
+    }
+}
+impl<T, S> VariadicHashSet<T, S> {
+    pub fn with_hasher(hasher: S) -> Self {
+        Self {
+            table: HashTable::new(),
+            hasher,
+        }
+    }
+    pub fn with_capacity_and_hasher(capacity: usize, hasher: S) -> Self {
+        Self {
+            table: HashTable::with_capacity(capacity),
+            hasher,
+        }
+    }
+}

variadics/src/lib.rs

@@ -11,6 +11,8 @@
 //! ## [`var_args!`]
 #![doc = include_str!("../var_args.md")]
 
+pub mod hash_set;
+
 use std::any::Any;
 
 use sealed::sealed;
@@ -481,7 +483,7 @@ impl CloneRefVariadic for () {
     fn clone_var(&self) -> Self::UnRefVar {}
 }
 
-/// A variadic where all item implement `PartialEq`.
+/// A variadic where all item implement [`PartialEq`].
 #[sealed]
 pub trait PartialEqVariadic: VariadicExt {
     /// `PartialEq` between a referenced variadic and a variadic of references, of the same types.