SOE ex.5.3
length' :: [a] -> Int
length' = sum . map (\_ -> 1)
length'' :: [a] -> Int
length'' = foldl (\acc _ -> acc + 1) 0
--length'' = foldr (\_ acc -> acc + 1) 0
length' :: [a] -> Int
length' = sum . map (\_ -> 1)
length'' :: [a] -> Int
length'' = foldl (\acc _ -> acc + 1) 0
--length'' = foldr (\_ acc -> acc + 1) 0