-- um Node é basicamente uma string, pra simplicidade do exemplo
newtype Node = Node String deriving (Show)
 
-- um grafo, em que cada Node liga outros Nodes com uma distância específica 
newtype Graph = Graph [(Node, [(Node, Int)])] deriving (Show)
 
-- um type alias para um algoritmo de busca
-- equivalente a uma interface de um método 
type GraphSearchFn = Graph -> String -> Maybe Node
 
-- implementações da interface
bfs :: GraphSearchFn 
bfs g v = Nothing
 
dfs :: GraphSearchFn 
dfs g v = Nothing
 
-- um ""método"" de Graph
search :: Graph -> GraphSearchFn -> String -> Maybe Node
search g f = f g
 
main :: IO ()
main = do
	let graph = Graph []
	let node = search graph dfs ""
	putStrLn $ show node
	return ()

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