Sketch HashMap impl.

sketching/september_2025/map/Map.dm

@@ -0,0 +1,58 @@
+pub trait HashCode
+    fn hash() -> USize
+end
+
+pub int Map<K, V>
+    fn get(key: K) -> Option<&V>
+    fn put(key: K, value: V) -> Void
+    fn take(key: K) -> Option<V>
+end
+
+pub class HashMap<K, V>(hasher: impl HashCode[K]) : Map<K, V>
+    
+    class Entry<K, V>(pub key: K, pub value: V) end
+    
+    let mut buckets: List<List<Entry<K, V>>> = ArrayList(size: 10, init: { [] })
+    
+    fn getBucketIndex(key: K) -> Int
+        hasher.hash(key) & buckets.size()
+    end
+    
+    impl fn put(key: K, value: V) -> Void
+        let bucket = buckets[getBucketIndex(key)]
+        bucket.add(Entry(key, value))
+    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>>
+        if bucket.findIndex { it.key == key } is Some(index) then
+            let entry = bucket.remove(index) // entry: Entry<K, V>
+            Some(entry.value) // moved out of Entry
+        else
+            None
+        end
+    end
+    
+end
+
+impl HashCode for String
+    fn hash() -> Int = todo()
+end
+
+class Greeter(pub greeting: String) end
+
+fn main()
+    let greeterMap: Map<String, Greeter> = HashMap(HashCode[]) // Short for HashCode[String]
+    greeterMap.put("friendly", Greeter("Friendly hello!"))
+    greeterMap.put("nasty", Greeter("Nasty hello!"))
+    let friendlyGreeter: &Greeter = greeterMap.get("friendly").unwrap()
+    println friendlyGreeter.greeting
+    let nastyGreeter: Greeter = greeterMap.take("nasty").unwrap()
+    println nastyGreeter.greeting
+end