Two implementations of a `findKey` function from Learn You a Haskell for Great Good. One uses explicit recursion the other a fold. The book recommends using fold for readability. But wouldn't using recursion be more efficient since the recursion halts as soon as an element is found?

fold-vs-recursion.hs

-- Recursion
findKey :: (Eq k) => k -> [(k,v)] -> Maybe v  
findKey key [] = Nothing  
findKey key ((k,v):xs) = if key == k  
                            then Just v  
                            else findKey key xs

-- Fold
findKey :: (Eq k) => k -> [(k,v)] -> Maybe v  
findKey key = foldr (\(k,v) acc -> if key == k then Just v else acc) Nothin

Answer from IRC: The right fold short-circuits due to Haskell being lazy so the two methods are practically equal. Very neat indeed!