Data.Map

opaque Map k v

A persistent mapping from ordered keys to values.

empty :: forall k v. Map k v

Construct an empty map.

insert :: forall k v. using (ord :: Ord k) => k -> v -> Map k v -> Map k v

Insert a value. An existing value at the same key is replaced.

lookup :: forall k v. using (ord :: Ord k) => k -> Map k v -> Option v

Find the value associated with a key.

lookup "port" (insert "port" 8080 empty)
-- Some 8080