findKey with fold

findKeyFoldr :: (Eq k) => k -> [(k,v)] -> Maybe v
findKeyFoldr key = foldr (\(k,v) acc -> if key == k then Just v else acc) Nothing

findKeyFoldl :: (Eq k) => k -> [(k,v)] -> Maybe v
findKeyFoldl key = foldl (\acc (k,v) -> if key == k then Just v else acc) Nothing