From 0d2db659cac210e4d1610263dffd58a7fd453e1a Mon Sep 17 00:00:00 2001
From: Jesse Brault <jbrault@mac.com>
Date: Wed, 24 Sep 2025 12:33:48 -0500
Subject: [PATCH] Work on Map sketching and related.

---
 sketching/september_2025/map/Map.dm | 166 +++++++++++++++++++++++++---
 1 file changed, 153 insertions(+), 13 deletions(-)

diff --git a/sketching/september_2025/map/Map.dm b/sketching/september_2025/map/Map.dm
index b25577b..da18ca5 100644
--- a/sketching/september_2025/map/Map.dm
+++ b/sketching/september_2025/map/Map.dm
@@ -1,3 +1,120 @@
+pub trait Functor<T>[Self<T>]
+    fn map(mapper: fn (t: &T) -> U) -> Self<U>
+end
+
+pub trait Sum<T>
+    fn sum() -> T
+end
+
+pub trait Default
+    fn default() -> Self
+end
+
+pub trait Iter<T>
+    ref fn iter() -> Iterator<&T>
+end
+
+pub trait ConsIter<T>
+    cons fn consIter() -> Iterator<T>
+end
+
+pub int Iterator<T>
+    fn next() -> Option<T>
+end
+
+pub int List<T> impl Functor<T>, Iter<T>, ConsIter<T>
+    fn add(t: T) -> Void
+end
+
+pub class ArrayList<T> : List<T>
+    let mut currentIndex = 0
+    let mut inner: Array<T>
+
+    ctor(capacity: Int) where T impl Default
+        inner = Array(capacity, Default[T])
+    end
+
+    ctor(capacity: Int, init: fn () -> T)
+        inner = Array(capacity, init)
+    end
+
+    impl fn add(t: T) -> Void
+        inner[currentIndex] = t
+        let currentCapacity = inner.capacity()
+        currentIndex++
+        if currentIndex == currentCapacity then
+            let oldInner = std::mem::take(inner, Array(currentCapacity * 2))
+            arrays::copy(oldInner, inner)
+        end
+    end
+end
+
+impl Functor[ArrayList<*>]
+    fn map(mapper: fn (t: &T) -> U) -> Self<U>
+        let mut result: Array<U> = Array(inner.capacity)
+        for (i, t) in inner.iterWithIndex() do
+            result[i] = mapper(t)
+        end
+        result
+    end
+end
+
+impl Sum[Self = List<Int>, T = Int]
+    fn sum() -> Int
+        let mut result = 0
+        for value in self do
+            result += value
+        end
+        result
+    end
+end
+
+impl<T impl Default> Default[ArrayList<T>]
+    const DEFAULT_SIZE = 10
+
+    static fn default() -> Self = ArrayList(DEFAULT_SIZE, Default[T]::default)
+end
+
+impl<T> Iter[ArrayList<T>]
+    ref fn iter() -> Iterator<&T>
+        let mut currentIndex = 0
+        return {
+            if currentIndex < inner.count() then
+                let item = inner[currentIndex]
+                currentIndex++
+                Some(item)
+            else
+                None
+            end
+        }
+    end
+end
+
+impl<T impl Default> ConsIter[ArrayList<T>]
+    cons fn consIter() -> Iterator<T>
+        let mut currentIndex = 0
+        let inner = std::mem::take(inner, std::arrays::empty())
+        return |inner| {
+            if currentIndex < inner.count() then
+                let item = inner.take(currentIndex, Default[T]::default)
+                currentIndex++
+                Some(item)
+            else
+                None
+            end
+        }
+    end
+end
+
+pub enum Option<T>
+    Some(t: T),
+    None
+end
+
+impl Default[Option<*>]
+    static fn default() -> Self = None
+end
+
 pub trait HashCode
     fn hash() -> USize
 end
@@ -8,37 +125,60 @@ pub int Map<K, V>
     fn take(key: K) -> Option<V>
 end
 
-pub class HashMap<K, V>(hasher: impl HashCode[K]) : Map<K, V>
-    
+pub class HashMap<K, V> : Map<K, V>
+    where K impl HashCode
+
+    const LOAD_FACTOR = 0.8
+
     class Entry<K, V>(pub key: K, pub value: V) end
-    
-    let mut buckets: List<List<Entry<K, V>>> = ArrayList(size: 10, init: { [] })
-    
+
+    let mut buckets: List<List<Option<Entry<K, V>>>> = ArrayList(10)
+
     fn getBucketIndex(key: K) -> Int
-        hasher.hash(key) & buckets.size()
+        HashCode[K].hash(key) % buckets.size()
     end
-    
+
+    fn getCount() -> Int = buckets.map { it.count() }.sum::<Int>()
+
+    fn getCapacity() -> Int = buckets.map { it.capacity() }.sum::<Int>()
+
+    fn redistribute()
+        use std::mem::take
+        let oldBucketCapacity = buckets.first().unwrap().capacity()
+        let oldBuckets = take(buckets, ArrayList(oldBucketCapacity * 2))
+        for bucket in oldBuckets.consIter() do
+            for entry in bucket.consIter() do
+                let newIndex = getBucketIndex(entry.key)
+                let newBucket = buckets[newIndex]
+                newBucket.add(Entry(entry.key, entry.value))
+            end
+        end
+    end
+
     impl fn put(key: K, value: V) -> Void
         let bucket = buckets[getBucketIndex(key)]
         bucket.add(Entry(key, value))
+        if getCount() / getCapacity() > LOAD_FACTOR then
+            redistribute()
+        end
     end
-    
+
     impl fn get(key: K) -> Option<&V>
         let bucket = buckets[getBucketIndex(key)] // bucket: &List<Entry<K, V>>
         bucket.find { it.key == key } // it: &Entry<K, V>
             .map { it.value } // it.value: &V
     end
-    
+
     impl fn take(key: K) -> Option<V>
-        let mut bucket = buckets.take(getBucketIndex(key), []) // bucket: List<Entry<K, V>>
+        let mut bucket = buckets.take(getBucketIndex(key)) // bucket: List<Entry<K, V>>
         if bucket.findIndex { it.key == key } is Some(index) then
-            let entry = bucket.remove(index) // entry: Entry<K, V>
+            let entry = bucket.take(index) // entry: Entry<K, V>
             Some(entry.value) // moved out of Entry
         else
             None
         end
     end
-    
+
 end
 
 impl HashCode for String
@@ -48,7 +188,7 @@ end
 class Greeter(pub greeting: String) end
 
 fn main()
-    let greeterMap: Map<String, Greeter> = HashMap(HashCode[]) // Short for HashCode[String]
+    let greeterMap: Map<String, Greeter> = HashMap()
     greeterMap.put("friendly", Greeter("Friendly hello!"))
     greeterMap.put("nasty", Greeter("Nasty hello!"))
     let friendlyGreeter: &Greeter = greeterMap.get("friendly").unwrap()