Refactoring for new types Map and Set, renaming of DisplacementSet and its methods. Builds, not tested.

src/gc.rs

@@ -197,6 +197,10 @@ impl<T,C> Traverse<C> for IdNode<T> where C: Allocates<Self> {
       IdNode::traverse(next,context)
     }
   }
+
+  fn collect(self) {
+    todo!()
+  }
 }
 
 #[derive(Clone)]

src/lib.rs

@@ -1,2 +1,10 @@
 pub mod gc;
 pub mod map;
+
+#[cfg(test)]
+mod tests {
+  #[test]
+  fn simple() {
+
+  }
+}

src/map.rs

@@ -18,8 +18,9 @@ Notes:
 - Values would only need to be shuffled around closer to their 'home' during a resize.
 - It is unlikely the displacement would large value without a resize amending that problem.
  */
-use std::hash::{DefaultHasher, Hash, Hasher};
 use crate::gc::{AnyId, Id};
+use std::fmt::Debug;
+use std::hash::{DefaultHasher, Hash, Hasher};
 
 type Displacement = u8;
 
@@ -70,70 +71,71 @@ impl Hashes for AnyId {
 }
 
 pub trait TableEntry: Equivalent<Self> + Hashes {
-  fn new_vacant() -> Self;
+    const VACANT: Self;
     fn is_vacant(&self) -> bool;
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug)]
-pub struct Entry<E> {
+pub struct Entry<E: TableEntry> {
     pub entry: E,
     home: usize,
     displacement: Displacement,
 }
 
-#[derive(Clone, Debug)]
+impl<E: TableEntry> Entry<E> {
-pub struct Map<E: TableEntry + Clone> {
+    const VACANT: Entry<E> = Entry {
+        entry: E::VACANT,
+        home: 0,
+        displacement: 0,
+    };
+}
+
+#[derive(Debug)]
+pub struct DisplacementSet<E: TableEntry> {
     // default representing vacancy!
     pub map: Vec<Entry<E>>, // todo: make this private and use an iterator
     map_bounds: std::ops::Range<usize>,
     map_count: usize, // number of elements in table
 }
 
-impl<E: TableEntry + Clone> Map<E> {
+impl<E: TableEntry> DisplacementSet<E> {
-  fn exchange_table(&mut self, len: usize) {
+    fn exchange(&mut self, len: usize) {
         let old = std::mem::replace(
             &mut self.map,
-      vec![
+            (0..len).map(|_| Entry::VACANT).collect(), // todo: I don't like that this may go over all memory
-        Entry {
-          entry: E::new_vacant(),
-          home: 0,
-          displacement: 0,
-        };
-        len
-      ],
         );
-    self.map_bounds = self.table_lower()..self.table_upper();
+        self.map_bounds = self.lower()..self.upper();
         for Entry { entry, .. } in old {
             if !entry.is_vacant() {
-        self.set_table(entry)
+                self.set(entry)
             }
         }
     }
-  pub fn resize_table(&mut self, len: usize) {
+    pub fn resize(&mut self, len: usize) {
-    self.exchange_table(len.max(self.map_count + (self.map_count / 3)));
+        self.exchange(len.max(self.map_count + (self.map_count / 3)));
-    self.map_bounds = 0..self.table_upper();
+        self.map_bounds = 0..self.upper();
     }
-  fn table_upper(&self) -> usize {
+    fn upper(&self) -> usize {
         (self.map.len() / 4) * 3
     }
-  fn table_lower(&self) -> usize {
+    fn lower(&self) -> usize {
         self.map.len() / 3
     }
-  fn ensure_table(&mut self) {
+    fn ensure(&mut self) {
-    if self.map_count + 1 > self.table_upper() {
+        if self.map_count + 1 > self.upper() {
             // free space is short
-      self.exchange_table((self.map.len() + 4) * 2);
+            self.exchange((self.map.len() + 4) * 2);
-    } else if self.map_count < self.table_lower() {
+        } else if self.map_count < self.lower() {
             // too much free space
-      self.exchange_table(self.map.len() / 2)
+            self.exchange(self.map.len() / 2)
         }
     }
-  pub fn set_table(&mut self, entry: E) {
+    pub fn set(&mut self, entry: E) {
         #[cfg(feature = "assertions")]
         assert!(!entry.is_vacant());
         if !self.map_bounds.contains(&(self.map_count + 1)) {
             // make sure the table is appropriately sized
-      self.ensure_table();
+            self.ensure();
         }
         let range = self.map.len();
         let home = entry.hashed() as usize % range;
@@ -197,11 +199,11 @@ impl<E: TableEntry + Clone> Map<E> {
             // must resize
             #[cfg(feature = "messages")]
             eprintln!("\n\tResizing...");
-      self.resize_table((self.map.len() + 4) * 2);
+            self.resize((self.map.len() + 4) * 2);
-      self.set_table(entry);
+            self.set(entry);
         }
     }
-  pub fn rem_table<K>(&mut self, index: K)
+    pub fn remove<K>(&mut self, index: K)
     where
         E: Equivalent<K>,
         K: Hashes,
@@ -212,7 +214,7 @@ impl<E: TableEntry + Clone> Map<E> {
         let range = self.map.len();
         let home = index.hashed() as usize % range;
         if self.map[home].entry.matches(&index) {
-      self.map[home].entry = E::new_vacant();
+            self.map[home].entry = E::VACANT;
             self.map_count -= 1;
         } else {
             if self.map[home].displacement != Displacement::MAX {
@@ -220,7 +222,7 @@ impl<E: TableEntry + Clone> Map<E> {
                 for i in 1..self.map[home].displacement {
                     let neighbour = &mut self.map[(home + i as usize) % range]; // todo: maybe mod slows this down
                     if neighbour.entry.matches(&index) {
-            neighbour.entry = E::new_vacant();
+                        neighbour.entry = E::VACANT;
                         self.map_count -= 1;
                         if i == self.map[home].displacement {
                             self.map[home].displacement = largest
@@ -237,7 +239,7 @@ impl<E: TableEntry + Clone> Map<E> {
                 for k in 0..self.map.len() {
                     let neighbour = &mut self.map[k];
                     if neighbour.entry.matches(&index) {
-            neighbour.entry = E::new_vacant();
+                        neighbour.entry = E::VACANT;
                         self.map_count -= 1;
                         #[cfg(feature = "assertions")]
                         {
@@ -261,7 +263,7 @@ impl<E: TableEntry + Clone> Map<E> {
             }
         }
     }
-  pub fn get_table<K>(&mut self, index: K) -> Option<&E>
+    pub fn get<K>(&mut self, index: K) -> Option<&E>
     where
         E: Equivalent<K>,
         K: Hashes,
@@ -283,8 +285,8 @@ impl<E: TableEntry + Clone> Map<E> {
             None
         }
     }
-  pub fn new() -> Map<E> {
+    pub fn new() -> DisplacementSet<E> {
-    Map {
+        DisplacementSet {
             map: Vec::new(),
             map_count: 0,
             map_bounds: (0..0).into(),
@@ -292,6 +294,116 @@ impl<E: TableEntry + Clone> Map<E> {
     }
 }
 
-pub struct TableEntry
+#[derive(Clone)]
+pub struct MapEntry<K: Hashes + PartialEq, V>(pub Option<(K, V)>);
 
-pub type Table<K,T> = Map<>
+impl<K: PartialEq + Hashes, V> Equivalent<K> for MapEntry<K, V> {
+    fn matches(&self, other: &K) -> bool {
+        &self.0.as_ref().unwrap().0 == other
+    }
+}
+
+impl<K: Hashes + PartialEq, V> Hashes for MapEntry<K, V> {
+    fn hashed(&self) -> Hashed {
+        self.0.as_ref().unwrap().0.hashed()
+    }
+}
+
+impl<K: Hashes + PartialEq, V> PartialEq for MapEntry<K, V> {
+    fn eq(&self, other: &Self) -> bool {
+        self.0.as_ref().unwrap().0 == other.0.as_ref().unwrap().0
+    }
+}
+
+impl<K: Hashes + PartialEq, V> TableEntry for MapEntry<K, V> {
+    const VACANT: Self = MapEntry(None);
+    fn is_vacant(&self) -> bool {
+        self.0.is_none()
+    }
+}
+
+pub struct Map<K: Hashes + PartialEq, V>(pub DisplacementSet<MapEntry<K, V>>);
+
+impl<K: Hashes + PartialEq, V> Map<K, V> {
+    pub fn resize(&mut self, len: usize) {
+        self.0.resize(len)
+    }
+    pub fn set(&mut self, index: K, value: V) {
+        self.0.set(MapEntry(Some((index, value))));
+    }
+    pub fn remove(&mut self, index: K) {
+        self.0.remove(index);
+    }
+    pub fn get(&mut self, index: K) -> Option<&V> {
+        if let Some(ref entry) = self.0.get(index) {
+            Some(&entry.0.as_ref().unwrap().1)
+        } else {
+            None
+        }
+    }
+    pub fn new() -> Map<K, V> {
+        Map(DisplacementSet::new())
+    }
+}
+
+impl<K: Debug + Hashes + PartialEq, V: Debug> Debug for Map<K, V> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_fmt(format_args!("Map")) // todo: debug and print the entire thing?
+    }
+}
+
+#[derive(PartialEq)]
+pub struct SetEntry<E: Hashes + PartialEq>(Option<E>);
+
+pub struct Set<E: Hashes + PartialEq>(DisplacementSet<SetEntry<E>>);
+
+impl<E: Hashes + PartialEq> Hashes for SetEntry<E> {
+    fn hashed(&self) -> Hashed {
+        todo!()
+    }
+}
+
+impl<E: Hashes + PartialEq> TableEntry for SetEntry<E> {
+    const VACANT: Self = SetEntry(None);
+    fn is_vacant(&self) -> bool {
+        self.0.is_none()
+    }
+}
+
+impl<E: Hashes + PartialEq> Equivalent<E> for SetEntry<E> {
+    fn matches(&self, other: &E) -> bool {
+        self.0.as_ref().unwrap() == other
+    }
+}
+
+impl<K, E: Hashes + PartialEq + Equivalent<K>> Equivalent<K> for SetEntry<E> {
+    fn matches(&self, other: &K) -> bool {
+        self.0.unwrap().matches(other)
+    }
+}
+
+impl<E: Hashes + PartialEq> Set<E> {
+    pub fn resize(&mut self, len: usize) {
+        self.0.resize(len)
+    }
+    pub fn set(&mut self, element: E) {
+        self.0.set(SetEntry(Some(element)));
+    }
+    pub fn remove(&mut self, element: E) {
+        self.0.remove(element);
+    }
+    pub fn get<K>(&mut self, element: K) -> Option<&E>
+    where
+        E: Equivalent<K>,
+        K: Hashes,
+    {
+        if let Some(ref entry) = self.0.get(element) {
+            Some(&entry.0.as_ref().unwrap())
+        } else {
+            None
+        }
+    }
+    pub fn new() -> Set<E> {
+        Set(DisplacementSet::new())
+    }
+}