feat: Ability to specify integer definitions

src/Data/Map/Implicit.hs

@@ -0,0 +1,22 @@
+{-# LANGUAGE Safe #-}
+{-# LANGUAGE TypeFamilies #-}
+--
+-- | A Map that derives the keys for the mapping from the items.
+
+module Data.Map.Implicit (ImplicitMap(), get, ImplicitKeyOf(..), empty) where
+import Data.Kind (Type, Constraint)
+import Data.Map (Map)
+import Data.Map qualified as Map
+
+type ImplicitMap :: Type -> Type
+type role ImplicitMap nominal
+newtype ImplicitMap v = ImplicitMap { get :: Map (KeyType v) v }
+
+type ImplicitKeyOf :: Type -> Constraint
+
+class ImplicitKeyOf v where
+  type KeyType v :: Type
+  keyOf :: v -> KeyType v
+
+empty :: ImplicitMap v
+empty = ImplicitMap Map.empty